21656251634997 has 32 divisors (see below), whose sum is σ = 33197353205760. Its totient is φ = 12301022865600.

The previous prime is 21656251634993. The next prime is 21656251634999. The reversal of 21656251634997 is 79943615265612.

It is a happy number.

It is not a de Polignac number, because 21656251634997 - 2² = 21656251634993 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21656251634993) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 17760204 + ... + 18940362.

It is an arithmetic number, because the mean of its divisors is an integer number (1037417287680).

Almost surely, 2^{21656251634997} is an apocalyptic number.

It is an amenable number.

21656251634997 is a deficient number, since it is larger than the sum of its proper divisors (11541101570763).

21656251634997 is a wasteful number, since it uses less digits than its factorization.

21656251634997 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1185393.

The product of its digits is 146966400, while the sum is 66.

The spelling of 21656251634997 in words is "twenty-one trillion, six hundred fifty-six billion, two hundred fifty-one million, six hundred thirty-four thousand, nine hundred ninety-seven".