81623661 has 48 divisors (see below), whose sum is σ = 134447040. Its totient is φ = 43841280.

The previous prime is 81623653. The next prime is 81623671. The reversal of 81623661 is 16632618.

It is not a de Polignac number, because 81623661 - 2³ = 81623653 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81623671) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 174550 + ... + 175016.

It is an arithmetic number, because the mean of its divisors is an integer number (2800980).

Almost surely, 2^81623661 is an apocalyptic number.

It is an amenable number.

81623661 is a deficient number, since it is larger than the sum of its proper divisors (52823379).

81623661 is a wasteful number, since it uses less digits than its factorization.

81623661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 554 (or 547 counting only the distinct ones).

The product of its digits is 10368, while the sum is 33.

The square root of 81623661 is about 9034.5813959475. The cubic root of 81623661 is about 433.7824959390.

The spelling of 81623661 in words is "eighty-one million, six hundred twenty-three thousand, six hundred sixty-one".