21551431355431 has 2 divisors, whose sum is σ = 21551431355432. Its totient is φ = 21551431355430.

The previous prime is 21551431355299. The next prime is 21551431355459. The reversal of 21551431355431 is 13455313415512.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21551431355431 - 2²³ = 21551422966823 is a prime.

It is a super-2 number, since 2×21551431355431² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21551431355471) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775715677715 + 10775715677716.

It is an arithmetic number, because the mean of its divisors is an integer number (10775715677716).

Almost surely, 2^{21551431355431} is an apocalyptic number.

21551431355431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21551431355431 is an equidigital number, since it uses as much as digits as its factorization.

21551431355431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 540000, while the sum is 43.

The spelling of 21551431355431 in words is "twenty-one trillion, five hundred fifty-one billion, four hundred thirty-one million, three hundred fifty-five thousand, four hundred thirty-one".