81509812 has 6 divisors (see below), whose sum is σ = 142642178. Its totient is φ = 40754904.

The previous prime is 81509809. The next prime is 81509833. The reversal of 81509812 is 21890518.

It can be written as a sum of positive squares in only one way, i.e., 58890276 + 22619536 = 7674^2 + 4756^2 .

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10188723 + ... + 10188730.

Almost surely, 2^81509812 is an apocalyptic number.

It is an amenable number.

81509812 is a deficient number, since it is larger than the sum of its proper divisors (61132366).

81509812 is a wasteful number, since it uses less digits than its factorization.

81509812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20377457 (or 20377455 counting only the distinct ones).

The product of its (nonzero) digits is 5760, while the sum is 34.

The square root of 81509812 is about 9028.2784626971. The cubic root of 81509812 is about 433.5807215935.

The spelling of 81509812 in words is "eighty-one million, five hundred nine thousand, eight hundred twelve".