81858664 has 8 divisors (see below), whose sum is σ = 153485010. Its totient is φ = 40929328.

The previous prime is 81858661. The next prime is 81858671. The reversal of 81858664 is 46685818.

It can be written as a sum of positive squares in only one way, i.e., 80245764 + 1612900 = 8958^2 + 1270^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is not an unprimeable number, because it can be changed into a prime (81858661) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5116159 + ... + 5116174.

Almost surely, 2^81858664 is an apocalyptic number.

It is an amenable number.

81858664 is a deficient number, since it is larger than the sum of its proper divisors (71626346).

81858664 is a wasteful number, since it uses less digits than its factorization.

81858664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10232339 (or 10232335 counting only the distinct ones).

The product of its digits is 368640, while the sum is 46.

The square root of 81858664 is about 9047.5777973997. The cubic root of 81858664 is about 434.1983986756.

The spelling of 81858664 in words is "eighty-one million, eight hundred fifty-eight thousand, six hundred sixty-four".