81623621 has 4 divisors (see below), whose sum is σ = 82841952. Its totient is φ = 80405292.

The previous prime is 81623617. The next prime is 81623627. The reversal of 81623621 is 12632618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12632618 = 2 ⋅6316309.

It is a cyclic number.

It is not a de Polignac number, because 81623621 - 2² = 81623617 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81623627) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 609065 + ... + 609198.

It is an arithmetic number, because the mean of its divisors is an integer number (20710488).

Almost surely, 2^81623621 is an apocalyptic number.

It is an amenable number.

81623621 is a deficient number, since it is larger than the sum of its proper divisors (1218331).

81623621 is a wasteful number, since it uses less digits than its factorization.

81623621 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1218330.

The product of its digits is 3456, while the sum is 29.

The square root of 81623621 is about 9034.5791822309. The cubic root of 81623621 is about 433.7824250800.

The spelling of 81623621 in words is "eighty-one million, six hundred twenty-three thousand, six hundred twenty-one".