81686620 has 24 divisors (see below), whose sum is σ = 177458400. Its totient is φ = 31547712.

The previous prime is 81686617. The next prime is 81686651. The reversal of 81686620 is 2668618.

It is a self number, because there is not a number n which added to its sum of digits gives 81686620.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 69840 + ... + 70999.

It is an arithmetic number, because the mean of its divisors is an integer number (7394100).

Almost surely, 2^81686620 is an apocalyptic number.

It is an amenable number.

81686620 is an abundant number, since it is smaller than the sum of its proper divisors (95771780).

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

81686620 is a wasteful number, since it uses less digits than its factorization.

81686620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 140877 (or 140875 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 37.

The square root of 81686620 is about 9038.0650584071. The cubic root of 81686620 is about 433.8939974857.

The spelling of 81686620 in words is "eighty-one million, six hundred eighty-six thousand, six hundred twenty".