81817644 has 12 divisors (see below), whose sum is σ = 190907864. Its totient is φ = 27272544.

The previous prime is 81817639. The next prime is 81817661. The reversal of 81817644 is 44671818.

It is a tau number, because it is divible by the number of its divisors (12).

It is a hoax number, since the sum of its digits (39) coincides with the sum of the digits of its distinct prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3409057 + ... + 3409080.

Almost surely, 2^81817644 is an apocalyptic number.

It is an amenable number.

81817644 is an abundant number, since it is smaller than the sum of its proper divisors (109090220).

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

81817644 is a wasteful number, since it uses less digits than its factorization.

81817644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6818144 (or 6818142 counting only the distinct ones).

The product of its digits is 43008, while the sum is 39.

The square root of 81817644 is about 9045.3106082655. The cubic root of 81817644 is about 434.1258598495.

The spelling of 81817644 in words is "eighty-one million, eight hundred seventeen thousand, six hundred forty-four".