81309756 has 48 divisors (see below), whose sum is σ = 207825408. Its totient is φ = 24537600.

The previous prime is 81309743. The next prime is 81309769. The reversal of 81309756 is 65790318.

It is an interprime number because it is at equal distance from previous prime (81309743) and next prime (81309769).

It is a super-2 number, since 2×81309756² = 13222552841559072, which contains 22 as substring.

It is a congruent number.

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, 34636 + ... + 36908.

It is an arithmetic number, because the mean of its divisors is an integer number (4329696).

Almost surely, 2^81309756 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 81309756, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103912704).

81309756 is an abundant number, since it is smaller than the sum of its proper divisors (126515652).

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

81309756 is a wasteful number, since it uses less digits than its factorization.

81309756 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2562 (or 2560 counting only the distinct ones).

The product of its (nonzero) digits is 45360, while the sum is 39.

The square root of 81309756 is about 9017.1922459267. The cubic root of 81309756 is about 433.2257071306.

The spelling of 81309756 in words is "eighty-one million, three hundred nine thousand, seven hundred fifty-six".