81299531 has 2 divisors, whose sum is σ = 81299532. Its totient is φ = 81299530.

The previous prime is 81299507. The next prime is 81299567. The reversal of 81299531 is 13599218.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 81299531 - 2¹⁰ = 81298507 is a prime.

It is a super-2 number, since 2×81299531² = 13219227481639922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (81299501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 40649765 + 40649766.

It is an arithmetic number, because the mean of its divisors is an integer number (40649766).

Almost surely, 2^81299531 is an apocalyptic number.

81299531 is a deficient number, since it is larger than the sum of its proper divisors (1).

81299531 is an equidigital number, since it uses as much as digits as its factorization.

81299531 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 19440, while the sum is 38.

The square root of 81299531 is about 9016.6252556042. The cubic root of 81299531 is about 433.2075464622.

The spelling of 81299531 in words is "eighty-one million, two hundred ninety-nine thousand, five hundred thirty-one".