81691200 has 336 divisors, whose sum is σ = 312440320. Its totient is φ = 20736000.

The previous prime is 81691177. The next prime is 81691243. The reversal of 81691200 is 219618.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1339170 + ... + 1339230.

Almost surely, 2^81691200 is an apocalyptic number.

81691200 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 81691200, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (156220160).

81691200 is an abundant number, since it is smaller than the sum of its proper divisors (230749120).

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

81691200 is a wasteful number, since it uses less digits than its factorization.

81691200 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 123 (or 102 counting only the distinct ones).

The product of its (nonzero) digits is 864, while the sum is 27.

The square root of 81691200 is about 9038.3184276723. The cubic root of 81691200 is about 433.9021065141.

The spelling of 81691200 in words is "eighty-one million, six hundred ninety-one thousand, two hundred".