81615812 has 6 divisors (see below), whose sum is σ = 142827678. Its totient is φ = 40807904.

The previous prime is 81615749. The next prime is 81615817. The reversal of 81615812 is 21851618.

It can be written as a sum of positive squares in only one way, i.e., 46022656 + 35593156 = 6784^2 + 5966^2 .

It is a super-2 number, since 2×81615812² = 13322281536838688, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (81615817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10201973 + ... + 10201980.

It is an arithmetic number, because the mean of its divisors is an integer number (23804613).

Almost surely, 2^81615812 is an apocalyptic number.

It is an amenable number.

81615812 is a deficient number, since it is larger than the sum of its proper divisors (61211866).

81615812 is a wasteful number, since it uses less digits than its factorization.

81615812 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20403957 (or 20403955 counting only the distinct ones).

The product of its digits is 3840, while the sum is 32.

The square root of 81615812 is about 9034.1469990254. The cubic root of 81615812 is about 433.7685911965.

The spelling of 81615812 in words is "eighty-one million, six hundred fifteen thousand, eight hundred twelve".