81643875 has 16 divisors (see below), whose sum is σ = 135856032. Its totient is φ = 43543200.

The previous prime is 81643853. The next prime is 81643897. The reversal of 81643875 is 57834618.

It is an interprime number because it is at equal distance from previous prime (81643853) and next prime (81643897).

It is not a de Polignac number, because 81643875 - 2²³ = 73255267 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 108484 + ... + 109233.

It is an arithmetic number, because the mean of its divisors is an integer number (8491002).

Almost surely, 2^81643875 is an apocalyptic number.

81643875 is a deficient number, since it is larger than the sum of its proper divisors (54212157).

81643875 is a wasteful number, since it uses less digits than its factorization.

81643875 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 217735 (or 217725 counting only the distinct ones).

The product of its digits is 161280, while the sum is 42.

The square root of 81643875 is about 9035.7000282214. The cubic root of 81643875 is about 433.8183015519.

The spelling of 81643875 in words is "eighty-one million, six hundred forty-three thousand, eight hundred seventy-five".