21616121656531 has 2 divisors, whose sum is σ = 21616121656532. Its totient is φ = 21616121656530.

The previous prime is 21616121656511. The next prime is 21616121656603. The reversal of 21616121656531 is 13565612161612.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21616121656531 - 2⁵ = 21616121656499 is a prime.

It is a super-2 number, since 2×21616121656531² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21616121656501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10808060828265 + 10808060828266.

It is an arithmetic number, because the mean of its divisors is an integer number (10808060828266).

Almost surely, 2^{21616121656531} is an apocalyptic number.

21616121656531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21616121656531 is an equidigital number, since it uses as much as digits as its factorization.

21616121656531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 388800, while the sum is 46.

The spelling of 21616121656531 in words is "twenty-one trillion, six hundred sixteen billion, one hundred twenty-one million, six hundred fifty-six thousand, five hundred thirty-one".