81311700 has 72 divisors (see below), whose sum is σ = 237172320. Its totient is φ = 21507200.

The previous prime is 81311683. The next prime is 81311723. The reversal of 81311700 is 711318.

It is a super-2 number, since 2×81311700² = 13223185113780000, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 38266 + ... + 40334.

It is an arithmetic number, because the mean of its divisors is an integer number (3294060).

Almost surely, 2^81311700 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 81311700, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (118586160).

81311700 is an abundant number, since it is smaller than the sum of its proper divisors (155860620).

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

81311700 is a wasteful number, since it uses less digits than its factorization.

81311700 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2217 (or 2210 counting only the distinct ones).

The product of its (nonzero) digits is 168, while the sum is 21.

The square root of 81311700 is about 9017.3000393688. The cubic root of 81311700 is about 433.2291597055.

The spelling of 81311700 in words is "eighty-one million, three hundred eleven thousand, seven hundred".