81564875 has 48 divisors (see below), whose sum is σ = 121447872. Its totient is φ = 53568000.

The previous prime is 81564863. The next prime is 81564887. The reversal of 81564875 is 57846518.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (81564863) and next prime (81564887).

It is not a de Polignac number, because 81564875 - 2¹² = 81560779 is a prime.

Its product of digits (268800) is a multiple of the sum of its prime divisors (140).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 840827 + ... + 840923.

It is an arithmetic number, because the mean of its divisors is an integer number (2530164).

Almost surely, 2^81564875 is an apocalyptic number.

81564875 is a deficient number, since it is larger than the sum of its proper divisors (39882997).

81564875 is an equidigital number, since it uses as much as digits as its factorization.

81564875 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 181 (or 140 counting only the distinct ones).

The product of its digits is 268800, while the sum is 44.

The square root of 81564875 is about 9031.3274218135. The cubic root of 81564875 is about 433.6783330782.

It can be divided in two parts, 8156 and 4875, that added together give a palindrome (13031).

The spelling of 81564875 in words is "eighty-one million, five hundred sixty-four thousand, eight hundred seventy-five".