81870381 has 24 divisors (see below), whose sum is σ = 124061184. Its totient is φ = 51965280.

The previous prime is 81870379. The next prime is 81870389. The reversal of 81870381 is 18307818.

It is not a de Polignac number, because 81870381 - 2¹ = 81870379 is a prime.

It is a super-2 number, since 2×81870381² = 13405518570170322, which contains 22 as substring.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81870389) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 13036 + ... + 18266.

It is an arithmetic number, because the mean of its divisors is an integer number (5169216).

Almost surely, 2^81870381 is an apocalyptic number.

It is an amenable number.

81870381 is a deficient number, since it is larger than the sum of its proper divisors (42190803).

81870381 is a wasteful number, since it uses less digits than its factorization.

81870381 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5321 (or 5318 counting only the distinct ones).

The product of its (nonzero) digits is 10752, while the sum is 36.

The square root of 81870381 is about 9048.2252956036. The cubic root of 81870381 is about 434.2191142996.

The spelling of 81870381 in words is "eighty-one million, eight hundred seventy thousand, three hundred eighty-one".