81312508 has 12 divisors (see below), whose sum is σ = 142681000. Its totient is φ = 40546512.

The previous prime is 81312503. The next prime is 81312551. The reversal of 81312508 is 80521318.

It is a super-2 number, since 2×81312508² = 13223447914500128, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81312503) 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, 25758 + ... + 28741.

Almost surely, 2^81312508 is an apocalyptic number.

It is an amenable number.

81312508 is a deficient number, since it is larger than the sum of its proper divisors (61368492).

81312508 is a wasteful number, since it uses less digits than its factorization.

81312508 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 54876 (or 54874 counting only the distinct ones).

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 81312508 is about 9017.3448420253. The cubic root of 81312508 is about 433.2305947101.

The spelling of 81312508 in words is "eighty-one million, three hundred twelve thousand, five hundred eight".