21521417155531 has 2 divisors, whose sum is σ = 21521417155532. Its totient is φ = 21521417155530.

The previous prime is 21521417155499. The next prime is 21521417155547. The reversal of 21521417155531 is 13555171412512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21521417155531 - 2⁵ = 21521417155499 is a prime.

It is a super-2 number, since 2×21521417155531² (a number of 27 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21521417155571) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10760708577765 + 10760708577766.

It is an arithmetic number, because the mean of its divisors is an integer number (10760708577766).

Almost surely, 2^{21521417155531} is an apocalyptic number.

21521417155531 is a deficient number, since it is larger than the sum of its proper divisors (1).

21521417155531 is an equidigital number, since it uses as much as digits as its factorization.

21521417155531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 210000, while the sum is 43.

The spelling of 21521417155531 in words is "twenty-one trillion, five hundred twenty-one billion, four hundred seventeen million, one hundred fifty-five thousand, five hundred thirty-one".