81635531 has 2 divisors, whose sum is σ = 81635532. Its totient is φ = 81635530.

The previous prime is 81635509. The next prime is 81635599. The reversal of 81635531 is 13553618.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81635531 - 2⁶ = 81635467 is a prime.

It is a super-2 number, since 2×81635531² = 13328719843303922, which contains 22 as substring.

It is a Sophie Germain prime.

It is not a weakly prime, because it can be changed into another prime (81635131) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40817765 + 40817766.

It is an arithmetic number, because the mean of its divisors is an integer number (40817766).

Almost surely, 2^81635531 is an apocalyptic number.

81635531 is a deficient number, since it is larger than the sum of its proper divisors (1).

81635531 is an equidigital number, since it uses as much as digits as its factorization.

81635531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10800, while the sum is 32.

The square root of 81635531 is about 9035.2382923750. The cubic root of 81635531 is about 433.8035223121.

The spelling of 81635531 in words is "eighty-one million, six hundred thirty-five thousand, five hundred thirty-one".