21256016651556 has 24 divisors (see below), whose sum is σ = 49604773862784. Its totient is φ = 7084281501600.

The previous prime is 21256016651501. The next prime is 21256016651579. The reversal of 21256016651556 is 65515661065212.

It is a super-2 number, since 2×21256016651556² (a number of 27 digits) contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21256016651499 and 21256016651508.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 132089020 + ... + 132249843.

It is an arithmetic number, because the mean of its divisors is an integer number (2066865577616).

Almost surely, 2^{21256016651556} is an apocalyptic number.

It is an amenable number.

21256016651556 is an abundant number, since it is smaller than the sum of its proper divisors (28348757211228).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21256016651556 is a wasteful number, since it uses less digits than its factorization.

21256016651556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 264345571 (or 264345569 counting only the distinct ones).

The product of its (nonzero) digits is 3240000, while the sum is 51.

The spelling of 21256016651556 in words is "twenty-one trillion, two hundred fifty-six billion, sixteen million, six hundred fifty-one thousand, five hundred fifty-six".