21400616857 has 4 divisors (see below), whose sum is σ = 21400921396. Its totient is φ = 21400312320.

The previous prime is 21400616843. The next prime is 21400616879. The reversal of 21400616857 is 75861600412.

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 can be written as a sum of positive squares in 2 ways, for example, as 14836214416 + 6564402441 = 121804^2 + 81021^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21400616857 is a prime.

It is a super-2 number, since 2×21400616857² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21400616257) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 12757 + ... + 207277.

It is an arithmetic number, because the mean of its divisors is an integer number (5350230349).

Almost surely, 2^21400616857 is an apocalyptic number.

It is an amenable number.

21400616857 is a deficient number, since it is larger than the sum of its proper divisors (304539).

21400616857 is a wasteful number, since it uses less digits than its factorization.

21400616857 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 304538.

The product of its (nonzero) digits is 80640, while the sum is 40.

The spelling of 21400616857 in words is "twenty-one billion, four hundred million, six hundred sixteen thousand, eight hundred fifty-seven".