81302440 has 16 divisors (see below), whose sum is σ = 182930580. Its totient is φ = 32520960.

The previous prime is 81302383. The next prime is 81302453. The reversal of 81302440 is 4420318.

It can be written as a sum of positive squares in 2 ways, for example, as 74615044 + 6687396 = 8638^2 + 2586^2 .

It is a super-2 number, since 2×81302440² = 13220173499907200, which contains 22 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1016241 + ... + 1016320.

Almost surely, 2^81302440 is an apocalyptic number.

It is an amenable number.

81302440 is an abundant number, since it is smaller than the sum of its proper divisors (101628140).

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

81302440 is a wasteful number, since it uses less digits than its factorization.

81302440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2032572 (or 2032568 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 22.

The square root of 81302440 is about 9016.7865672866. The cubic root of 81302440 is about 433.2127133051.

Adding to 81302440 its reverse (4420318), we get a palindrome (85722758).

The spelling of 81302440 in words is "eighty-one million, three hundred two thousand, four hundred forty".