81626440 has 64 divisors (see below), whose sum is σ = 215596800. Its totient is φ = 27226368.

The previous prime is 81626431. The next prime is 81626443. The reversal of 81626440 is 4462618.

It is not an unprimeable number, because it can be changed into a prime (81626443) 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, 6421 + ... + 14299.

It is an arithmetic number, because the mean of its divisors is an integer number (3368700).

Almost surely, 2^81626440 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 81626440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (107798400).

81626440 is an abundant number, since it is smaller than the sum of its proper divisors (133970360).

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

81626440 is a wasteful number, since it uses less digits than its factorization.

81626440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7934 (or 7930 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 31.

The square root of 81626440 is about 9034.7351925776. The cubic root of 81626440 is about 433.7874188084.

The spelling of 81626440 in words is "eighty-one million, six hundred twenty-six thousand, four hundred forty".