81557925 has 48 divisors (see below), whose sum is σ = 145919232. Its totient is φ = 40038400.

The previous prime is 81557923. The next prime is 81557933. The reversal of 81557925 is 52975518.

It is not a de Polignac number, because 81557925 - 2¹ = 81557923 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 (81557921) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 59245 + ... + 60605.

It is an arithmetic number, because the mean of its divisors is an integer number (3039984).

Almost surely, 2^81557925 is an apocalyptic number.

81557925 is a gapful number since it is divisible by the number (85) formed by its first and last digit.

It is an amenable number.

81557925 is a deficient number, since it is larger than the sum of its proper divisors (64361307).

81557925 is a wasteful number, since it uses less digits than its factorization.

81557925 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1438 (or 1433 counting only the distinct ones).

The product of its digits is 126000, while the sum is 42.

The square root of 81557925 is about 9030.9426418287. The cubic root of 81557925 is about 433.6660150716. Note that the first 3 decimals are identical.

The spelling of 81557925 in words is "eighty-one million, five hundred fifty-seven thousand, nine hundred twenty-five".