81619644 has 12 divisors (see below), whose sum is σ = 190445864. Its totient is φ = 27206544.

The previous prime is 81619613. The next prime is 81619723. The reversal of 81619644 is 44691618.

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

It is a congruent number.

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, 3400807 + ... + 3400830.

Almost surely, 2^81619644 is an apocalyptic number.

It is an amenable number.

81619644 is an abundant number, since it is smaller than the sum of its proper divisors (108826220).

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

81619644 is a wasteful number, since it uses less digits than its factorization.

81619644 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6801644 (or 6801642 counting only the distinct ones).

The product of its digits is 41472, while the sum is 39.

The square root of 81619644 is about 9034.3590807539. The cubic root of 81619644 is about 433.7753798126.

The spelling of 81619644 in words is "eighty-one million, six hundred nineteen thousand, six hundred forty-four".