21056140157809 has 3 divisors (see below), whose sum is σ = 21056144746507. Its totient is φ = 21056135569112.

The previous prime is 21056140157797. The next prime is 21056140157821. The reversal of 21056140157809 is 90875104165012.

The square root of 21056140157809 is 4588697.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is an interprime number because it is at equal distance from previous prime (21056140157797) and next prime (21056140157821).

It can be written as a sum of positive squares in only one way, i.e., 900781319025 + 20155358838784 = 949095^2 + 4489472^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21056140157809 is a prime.

It is a super-2 number, since 2×21056140157809² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21056140167809) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 2294349 + ... + 6883045.

Almost surely, 2^{21056140157809} is an apocalyptic number.

21056140157809 is the 4588697-th square number.

21056140157809 is the 2294349-th centered octagonal number.

It is an amenable number.

21056140157809 is a deficient number, since it is larger than the sum of its proper divisors (4588698).

21056140157809 is an frugal number, since it uses more digits than its factorization.

21056140157809 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9177394 (or 4588697 counting only the distinct ones).

The product of its (nonzero) digits is 604800, while the sum is 49.

The spelling of 21056140157809 in words is "twenty-one trillion, fifty-six billion, one hundred forty million, one hundred fifty-seven thousand, eight hundred nine".