81305788 has 48 divisors (see below), whose sum is σ = 155584800. Its totient is φ = 37048320.

The previous prime is 81305771. The next prime is 81305789. The reversal of 81305788 is 88750318.

It is a super-2 number, since 2×81305788² = 13221262324601888, 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 81305788.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81305789) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 302118 + ... + 302386.

It is an arithmetic number, because the mean of its divisors is an integer number (3241350).

Almost surely, 2^81305788 is an apocalyptic number.

It is an amenable number.

81305788 is a deficient number, since it is larger than the sum of its proper divisors (74279012).

81305788 is a wasteful number, since it uses less digits than its factorization.

81305788 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 430 (or 428 counting only the distinct ones).

The product of its (nonzero) digits is 53760, while the sum is 40.

The square root of 81305788 is about 9016.9722190988. The cubic root of 81305788 is about 433.2186597288.

The spelling of 81305788 in words is "eighty-one million, three hundred five thousand, seven hundred eighty-eight".