81637381 has 12 divisors (see below), whose sum is σ = 95376960. Its totient is φ = 69672120.

The previous prime is 81637379. The next prime is 81637393. The reversal of 81637381 is 18373618.

It is not a de Polignac number, because 81637381 - 2¹ = 81637379 is a prime.

It is a super-2 number, since 2×81637381² = 13329323953078322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 81637381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81637321) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 8226 + ... + 15196.

It is an arithmetic number, because the mean of its divisors is an integer number (7948080).

Almost surely, 2^81637381 is an apocalyptic number.

It is an amenable number.

81637381 is a deficient number, since it is larger than the sum of its proper divisors (13739579).

81637381 is a wasteful number, since it uses less digits than its factorization.

81637381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7224 (or 7217 counting only the distinct ones).

The product of its digits is 24192, while the sum is 37.

The square root of 81637381 is about 9035.3406687297. The cubic root of 81637381 is about 433.8067991959.

The spelling of 81637381 in words is "eighty-one million, six hundred thirty-seven thousand, three hundred eighty-one".