81557975 has 24 divisors (see below), whose sum is σ = 107552640. Its totient is φ = 61175520.

The previous prime is 81557963. The next prime is 81557999. The reversal of 81557975 is 57975518.

It is a happy number.

It is not a de Polignac number, because 81557975 - 2⁸ = 81557719 is a prime.

It is a super-2 number, since 2×81557975² = 13303406572201250, which contains 22 as substring.

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 23 ways as a sum of consecutive naturals, for example, 48092 + ... + 49758.

It is an arithmetic number, because the mean of its divisors is an integer number (4481360).

Almost surely, 2^81557975 is an apocalyptic number.

81557975 is a deficient number, since it is larger than the sum of its proper divisors (25994665).

81557975 is a wasteful number, since it uses less digits than its factorization.

81557975 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1799 (or 1794 counting only the distinct ones).

The product of its digits is 441000, while the sum is 47.

The square root of 81557975 is about 9030.9454100886. The cubic root of 81557975 is about 433.6661036928. Note that the first 3 decimals are identical.

The spelling of 81557975 in words is "eighty-one million, five hundred fifty-seven thousand, nine hundred seventy-five".