81680554 has 4 divisors (see below), whose sum is σ = 122520834. Its totient is φ = 40840276.

The previous prime is 81680531. The next prime is 81680593. The reversal of 81680554 is 45508618.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 45508618 = 2 ⋅22754309.

It can be written as a sum of positive squares in only one way, i.e., 79655625 + 2024929 = 8925^2 + 1423^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20420137 + ... + 20420140.

Almost surely, 2^81680554 is an apocalyptic number.

81680554 is a deficient number, since it is larger than the sum of its proper divisors (40840280).

81680554 is a wasteful number, since it uses less digits than its factorization.

81680554 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40840279.

The product of its (nonzero) digits is 38400, while the sum is 37.

The square root of 81680554 is about 9037.7294714989. The cubic root of 81680554 is about 433.8832569827.

The spelling of 81680554 in words is "eighty-one million, six hundred eighty thousand, five hundred fifty-four".