81313128 has 96 divisors (see below), whose sum is σ = 239639400. Its totient is φ = 24758784.

The previous prime is 81313117. The next prime is 81313139. The reversal of 81313128 is 82131318.

81313128 is a nontrivial binomial coefficient, being equal to C(12753, 2).

It is an interprime number because it is at equal distance from previous prime (81313117) and next prime (81313139).

It can be written as a sum of positive squares in 4 ways, for example, as 63011844 + 18301284 = 7938^2 + 4278^2 .

It is a super-2 number, since 2×81313128² = 13223649570288768, which contains 22 as substring.

It is a nude number because it is divisible by every one of its digits.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 101626 + ... + 102422.

Almost surely, 2^81313128 is an apocalyptic number.

81313128 is the 12752-nd triangular number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81313128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (119819700).

81313128 is an abundant number, since it is smaller than the sum of its proper divisors (158326272).

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

81313128 is a wasteful number, since it uses less digits than its factorization.

81313128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 931 (or 924 counting only the distinct ones).

The product of its digits is 1152, while the sum is 27.

The square root of 81313128 is about 9017.3792201504. The cubic root of 81313128 is about 433.2316958211.

The spelling of 81313128 in words is "eighty-one million, three hundred thirteen thousand, one hundred twenty-eight".