81371720 has 32 divisors (see below), whose sum is σ = 183470400. Its totient is φ = 32480448.

The previous prime is 81371671. The next prime is 81371747. The reversal of 81371720 is 2717318.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 20021 + ... + 23739.

It is an arithmetic number, because the mean of its divisors is an integer number (5733450).

Almost surely, 2^81371720 is an apocalyptic number.

It is an amenable number.

81371720 is an abundant number, since it is smaller than the sum of its proper divisors (102098680).

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

81371720 is a wasteful number, since it uses less digits than its factorization.

81371720 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4277 (or 4273 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 29.

The square root of 81371720 is about 9020.6274726318. The cubic root of 81371720 is about 433.3357291123.

The spelling of 81371720 in words is "eighty-one million, three hundred seventy-one thousand, seven hundred twenty".