81308506 has 4 divisors (see below), whose sum is σ = 121962762. Its totient is φ = 40654252.

The previous prime is 81308477. The next prime is 81308527. The reversal of 81308506 is 60580318.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 60580318 = 2 ⋅30290159.

It can be written as a sum of positive squares in only one way, i.e., 72846225 + 8462281 = 8535^2 + 2909^2 .

It is a super-2 number, since 2×81308506² = 13222146295904072, which contains 22 as substring.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 20327125 + ... + 20327128.

Almost surely, 2^81308506 is an apocalyptic number.

81308506 is a deficient number, since it is larger than the sum of its proper divisors (40654256).

81308506 is a wasteful number, since it uses less digits than its factorization.

81308506 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40654255.

The product of its (nonzero) digits is 5760, while the sum is 31.

The square root of 81308506 is about 9017.1229336191. The cubic root of 81308506 is about 433.2234870817.

The spelling of 81308506 in words is "eighty-one million, three hundred eight thousand, five hundred six".