81391870 has 16 divisors (see below), whose sum is σ = 167434848. Its totient is φ = 27905760.

The previous prime is 81391859. The next prime is 81391889. The reversal of 81391870 is 7819318.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 581301 + ... + 581440.

It is an arithmetic number, because the mean of its divisors is an integer number (10464678).

Almost surely, 2^81391870 is an apocalyptic number.

81391870 is an abundant number, since it is smaller than the sum of its proper divisors (86042978).

81391870 is a wasteful number, since it uses less digits than its factorization.

81391870 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1162755.

The product of its (nonzero) digits is 12096, while the sum is 37.

The square root of 81391870 is about 9021.7442881075. The cubic root of 81391870 is about 433.3714949955.

The spelling of 81391870 in words is "eighty-one million, three hundred ninety-one thousand, eight hundred seventy".