81557523 has 10 divisors (see below), whose sum is σ = 121832964. Its totient is φ = 54371628.

The previous prime is 81557479. The next prime is 81557537. The reversal of 81557523 is 32575518.

81557523 is a `hidden beast` number, since 81 + 5 + 57 + 523 = 666.

It is not a de Polignac number, because 81557523 - 2⁶ = 81557459 is a prime.

It is a super-3 number, since 3×81557523³ (a number of 25 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (81557123) 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 9 ways as a sum of consecutive naturals, for example, 503361 + ... + 503522.

Almost surely, 2^81557523 is an apocalyptic number.

81557523 is a deficient number, since it is larger than the sum of its proper divisors (40275441).

81557523 is a wasteful number, since it uses less digits than its factorization.

81557523 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1006895 (or 1006886 counting only the distinct ones).

The product of its digits is 42000, while the sum is 36.

The square root of 81557523 is about 9030.9203849885. The cubic root of 81557523 is about 433.6653025554.

The spelling of 81557523 in words is "eighty-one million, five hundred fifty-seven thousand, five hundred twenty-three".