81571557 has 16 divisors (see below), whose sum is σ = 110522880. Its totient is φ = 53507952.

The previous prime is 81571531. The next prime is 81571561. The reversal of 81571557 is 75517518.

It is a happy number.

It is not a de Polignac number, because 81571557 - 2¹⁵ = 81538789 is a prime.

It is a super-2 number, since 2×81571557² = 13307837822808498, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81571507) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 51544 + ... + 53102.

It is an arithmetic number, because the mean of its divisors is an integer number (6907680).

Almost surely, 2^81571557 is an apocalyptic number.

It is an amenable number.

81571557 is a deficient number, since it is larger than the sum of its proper divisors (28951323).

81571557 is a wasteful number, since it uses less digits than its factorization.

81571557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1832.

The product of its digits is 49000, while the sum is 39.

The square root of 81571557 is about 9031.6973487822. The cubic root of 81571557 is about 433.6901754286.

It can be divided in two parts, 81571 and 557, that added together give a palindrome (82128).

The spelling of 81571557 in words is "eighty-one million, five hundred seventy-one thousand, five hundred fifty-seven".