21021031329581 has 2 divisors, whose sum is σ = 21021031329582. Its totient is φ = 21021031329580.

The previous prime is 21021031329521. The next prime is 21021031329593. The reversal of 21021031329581 is 18592313012012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20839270650025 + 181760679556 = 4565005^2 + 426334^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21021031329581 is a prime.

It is a super-2 number, since 2×21021031329581² (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 (21021031329511) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510515664790 + 10510515664791.

It is an arithmetic number, because the mean of its divisors is an integer number (10510515664791).

Almost surely, 2^{21021031329581} is an apocalyptic number.

It is an amenable number.

21021031329581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021031329581 is an equidigital number, since it uses as much as digits as its factorization.

21021031329581 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 25920, while the sum is 38.

The spelling of 21021031329581 in words is "twenty-one trillion, twenty-one billion, thirty-one million, three hundred twenty-nine thousand, five hundred eighty-one".