81508690 has 8 divisors (see below), whose sum is σ = 146715660. Its totient is φ = 32603472.

The previous prime is 81508633. The next prime is 81508699. The reversal of 81508690 is 9680518.

It can be written as a sum of positive squares in 2 ways, for example, as 72812089 + 8696601 = 8533^2 + 2949^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a super-2 number, since 2×81508690² = 13287333091032200, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81508699) 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, 4075425 + ... + 4075444.

Almost surely, 2^81508690 is an apocalyptic number.

81508690 is a deficient number, since it is larger than the sum of its proper divisors (65206970).

81508690 is a wasteful number, since it uses less digits than its factorization.

81508690 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8150876.

The product of its (nonzero) digits is 17280, while the sum is 37.

The square root of 81508690 is about 9028.2163243910. The cubic root of 81508690 is about 433.5787321406.

The spelling of 81508690 in words is "eighty-one million, five hundred eight thousand, six hundred ninety".