81305812 has 24 divisors (see below), whose sum is σ = 162852480. Its totient is φ = 34793760.

The previous prime is 81305797. The next prime is 81305827. The reversal of 81305812 is 21850318.

It is an interprime number because it is at equal distance from previous prime (81305797) and next prime (81305827).

It is a super-2 number, since 2×81305812² = 13221270129958688, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (28).

It is a congruent number.

It is an unprimeable number.

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 in 7 ways as a sum of consecutive naturals, for example, 21762 + ... + 25222.

It is an arithmetic number, because the mean of its divisors is an integer number (6785520).

Almost surely, 2^81305812 is an apocalyptic number.

It is an amenable number.

81305812 is an abundant number, since it is smaller than the sum of its proper divisors (81546668).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81305812 is a wasteful number, since it uses less digits than its factorization.

81305812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4311 (or 4309 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 81305812 is about 9016.9735499224. The cubic root of 81305812 is about 433.2187023549.

The spelling of 81305812 in words is "eighty-one million, three hundred five thousand, eight hundred twelve".