21256042163431 has 2 divisors, whose sum is σ = 21256042163432. Its totient is φ = 21256042163430.

The previous prime is 21256042163399. The next prime is 21256042163441. The reversal of 21256042163431 is 13436124065212.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21256042163431 - 2⁵ = 21256042163399 is a prime.

It is a super-2 number, since 2×21256042163431² (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 (21256042163441) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10628021081715 + 10628021081716.

It is an arithmetic number, because the mean of its divisors is an integer number (10628021081716).

Almost surely, 2^{21256042163431} is an apocalyptic number.

21256042163431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21256042163431 is an equidigital number, since it uses as much as digits as its factorization.

21256042163431 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 207360, while the sum is 40.

The spelling of 21256042163431 in words is "twenty-one trillion, two hundred fifty-six billion, forty-two million, one hundred sixty-three thousand, four hundred thirty-one".