81990074 has 4 divisors (see below), whose sum is σ = 122985114. Its totient is φ = 40995036.

The previous prime is 81990059. The next prime is 81990089. The reversal of 81990074 is 47009918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 47009918 = 2 ⋅23504959.

It is an interprime number because it is at equal distance from previous prime (81990059) and next prime (81990089).

It can be written as a sum of positive squares in only one way, i.e., 67980025 + 14010049 = 8245^2 + 3743^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20497517 + ... + 20497520.

Almost surely, 2^81990074 is an apocalyptic number.

81990074 is a deficient number, since it is larger than the sum of its proper divisors (40995040).

81990074 is a wasteful number, since it uses less digits than its factorization.

81990074 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40995039.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 81990074 is about 9054.8370498867. The cubic root of 81990074 is about 434.4306180633.

The spelling of 81990074 in words is "eighty-one million, nine hundred ninety thousand, seventy-four".