21005715457 has 8 divisors (see below), whose sum is σ = 22243221000. Its totient is φ = 19768418304.

The previous prime is 21005715439. The next prime is 21005715461. The reversal of 21005715457 is 75451750012.

It can be written as a sum of positive squares in 4 ways, for example, as 7252055281 + 13753660176 = 85159^2 + 117276^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21005715457 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21005715407) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 186769 + ... + 277297.

It is an arithmetic number, because the mean of its divisors is an integer number (2780402625).

Almost surely, 2^21005715457 is an apocalyptic number.

It is an amenable number.

21005715457 is a deficient number, since it is larger than the sum of its proper divisors (1237505543).

21005715457 is a wasteful number, since it uses less digits than its factorization.

21005715457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104195.

The product of its (nonzero) digits is 49000, while the sum is 37.

The spelling of 21005715457 in words is "twenty-one billion, five million, seven hundred fifteen thousand, four hundred fifty-seven".