81309624 has 64 divisors (see below), whose sum is σ = 226506240. Its totient is φ = 24111360.

The previous prime is 81309619. The next prime is 81309629. The reversal of 81309624 is 42690318.

It is an interprime number because it is at equal distance from previous prime (81309619) and next prime (81309629).

It is a super-2 number, since 2×81309624² = 13222509910042752, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81309629) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 9132 + ... + 15684.

It is an arithmetic number, because the mean of its divisors is an integer number (3539160).

Almost surely, 2^81309624 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 81309624, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (113253120).

81309624 is an abundant number, since it is smaller than the sum of its proper divisors (145196616).

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

81309624 is a wasteful number, since it uses less digits than its factorization.

81309624 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6620 (or 6616 counting only the distinct ones).

The product of its (nonzero) digits is 10368, while the sum is 33.

The square root of 81309624 is about 9017.1849265722. The cubic root of 81309624 is about 433.2254726945.

The spelling of 81309624 in words is "eighty-one million, three hundred nine thousand, six hundred twenty-four".