81681670 has 32 divisors (see below), whose sum is σ = 168364800. Its totient is φ = 27949536.

The previous prime is 81681659. The next prime is 81681679. The reversal of 81681670 is 7618618.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81681679) 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, 50941 + ... + 52519.

It is an arithmetic number, because the mean of its divisors is an integer number (5261400).

Almost surely, 2^81681670 is an apocalyptic number.

81681670 is an abundant number, since it is smaller than the sum of its proper divisors (86683130).

81681670 is a wasteful number, since it uses less digits than its factorization.

81681670 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2332.

The product of its (nonzero) digits is 16128, while the sum is 37.

The square root of 81681670 is about 9037.7912124589. The cubic root of 81681670 is about 433.8852330202.

The spelling of 81681670 in words is "eighty-one million, six hundred eighty-one thousand, six hundred seventy".