81564624 has 80 divisors (see below), whose sum is σ = 244329600. Its totient is φ = 26002944.

The previous prime is 81564611. The next prime is 81564629. The reversal of 81564624 is 42646518.

81564624 is a `hidden beast` number, since 8 + 1 + 5 + 646 + 2 + 4 = 666.

It is a super-2 number, since 2×81564624² = 13305575776522752, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81564629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5832 + ... + 14040.

It is an arithmetic number, because the mean of its divisors is an integer number (3054120).

Almost surely, 2^81564624 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 81564624, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (122164800).

81564624 is an abundant number, since it is smaller than the sum of its proper divisors (162764976).

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

81564624 is a wasteful number, since it uses less digits than its factorization.

81564624 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8249 (or 8237 counting only the distinct ones).

The product of its digits is 46080, while the sum is 36.

The square root of 81564624 is about 9031.3135257281. The cubic root of 81564624 is about 433.6778882243.

The spelling of 81564624 in words is "eighty-one million, five hundred sixty-four thousand, six hundred twenty-four".