81491784 has 32 divisors (see below), whose sum is σ = 222251040. Its totient is φ = 24694400.

The previous prime is 81491771. The next prime is 81491801. The reversal of 81491784 is 48719418.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 154077 + ... + 154604.

It is an arithmetic number, because the mean of its divisors is an integer number (6945345).

Almost surely, 2^81491784 is an apocalyptic number.

It is an amenable number.

81491784 is an abundant number, since it is smaller than the sum of its proper divisors (140759256).

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

81491784 is a wasteful number, since it uses less digits than its factorization.

81491784 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 308701 (or 308697 counting only the distinct ones).

The product of its digits is 64512, while the sum is 42.

The square root of 81491784 is about 9027.2799890111. The cubic root of 81491784 is about 433.5487533785.

The spelling of 81491784 in words is "eighty-one million, four hundred ninety-one thousand, seven hundred eighty-four".