81910531 has 2 divisors, whose sum is σ = 81910532. Its totient is φ = 81910530.

The previous prime is 81910523. The next prime is 81910547. The reversal of 81910531 is 13501918.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81910531 - 2³ = 81910523 is a prime.

It is a super-2 number, since 2×81910531² = 13418670177403922, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81910531.

It is not a weakly prime, because it can be changed into another prime (81910831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40955265 + 40955266.

It is an arithmetic number, because the mean of its divisors is an integer number (40955266).

Almost surely, 2^81910531 is an apocalyptic number.

81910531 is a deficient number, since it is larger than the sum of its proper divisors (1).

81910531 is an equidigital number, since it uses as much as digits as its factorization.

81910531 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1080, while the sum is 28.

The square root of 81910531 is about 9050.4436907811. The cubic root of 81910531 is about 434.2900844034.

The spelling of 81910531 in words is "eighty-one million, nine hundred ten thousand, five hundred thirty-one".