81358872 has 128 divisors (see below), whose sum is σ = 250698240. Its totient is φ = 21473280.

The previous prime is 81358859. The next prime is 81358873. The reversal of 81358872 is 27885318.

It is a happy number.

It is a super-2 number, since 2×81358872² = 13238532106224768, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (42).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81358873) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 173983 + ... + 174449.

It is an arithmetic number, because the mean of its divisors is an integer number (1958580).

Almost surely, 2^81358872 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81358872, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (125349120).

81358872 is an abundant number, since it is smaller than the sum of its proper divisors (169339368).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

81358872 is a wasteful number, since it uses less digits than its factorization.

81358872 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 561 (or 557 counting only the distinct ones).

The product of its digits is 107520, while the sum is 42.

The square root of 81358872 is about 9019.9152989371. The cubic root of 81358872 is about 433.3129210635.

It can be divided in two parts, 813 and 58872, that added together give a triangular number (59685 = T₃₄₅).

The spelling of 81358872 in words is "eighty-one million, three hundred fifty-eight thousand, eight hundred seventy-two".