81840660 has 48 divisors (see below), whose sum is σ = 249988032. Its totient is φ = 19840000.

The previous prime is 81840659. The next prime is 81840667. The reversal of 81840660 is 6604818.

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 (81840667) 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, 61341 + ... + 62660.

It is an arithmetic number, because the mean of its divisors is an integer number (5208084).

Almost surely, 2^81840660 is an apocalyptic number.

It is an amenable number.

81840660 is an abundant number, since it is smaller than the sum of its proper divisors (168147372).

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

81840660 is a wasteful number, since it uses less digits than its factorization.

81840660 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 124024 (or 124022 counting only the distinct ones).

The product of its (nonzero) digits is 9216, while the sum is 33.

The square root of 81840660 is about 9046.5827802547. The cubic root of 81840660 is about 434.1665638000.

The spelling of 81840660 in words is "eighty-one million, eight hundred forty thousand, six hundred sixty".