81891960 has 64 divisors (see below), whose sum is σ = 256366080. Its totient is φ = 20887680.

The previous prime is 81891949. The next prime is 81891961. The reversal of 81891960 is 6919818.

It is a super-2 number, since 2×81891960² = 13412586225283200, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81891961) 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, 12076 + ... + 17595.

It is an arithmetic number, because the mean of its divisors is an integer number (4005720).

Almost surely, 2^81891960 is an apocalyptic number.

It is an amenable number.

81891960 is an abundant number, since it is smaller than the sum of its proper divisors (174474120).

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

81891960 is a wasteful number, since it uses less digits than its factorization.

81891960 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 29708 (or 29704 counting only the distinct ones).

The product of its (nonzero) digits is 31104, while the sum is 42.

The square root of 81891960 is about 9049.4176608222. The cubic root of 81891960 is about 434.2572607413.

The spelling of 81891960 in words is "eighty-one million, eight hundred ninety-one thousand, nine hundred sixty".