81379725 has 24 divisors (see below), whose sum is σ = 153769920. Its totient is φ = 37201920.

The previous prime is 81379723. The next prime is 81379733. The reversal of 81379725 is 52797318.

It is not a de Polignac number, because 81379725 - 2¹ = 81379723 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81379723) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 76980 + ... + 78029.

It is an arithmetic number, because the mean of its divisors is an integer number (6407080).

Almost surely, 2^81379725 is an apocalyptic number.

It is an amenable number.

81379725 is a deficient number, since it is larger than the sum of its proper divisors (72390195).

81379725 is a wasteful number, since it uses less digits than its factorization.

81379725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 155029 (or 155024 counting only the distinct ones).

The product of its digits is 105840, while the sum is 42.

The square root of 81379725 is about 9021.0711669956. The cubic root of 81379725 is about 433.3499385484.

The spelling of 81379725 in words is "eighty-one million, three hundred seventy-nine thousand, seven hundred twenty-five".