81328557 has 8 divisors (see below), whose sum is σ = 112177440. Its totient is φ = 52349360.

The previous prime is 81328537. The next prime is 81328567. The reversal of 81328557 is 75582318.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 81328557 - 2¹² = 81324461 is a prime.

It is a super-2 number, since 2×81328557² = 13228668367404498, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (81328537) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 467319 + ... + 467492.

It is an arithmetic number, because the mean of its divisors is an integer number (14022180).

Almost surely, 2^81328557 is an apocalyptic number.

81328557 is a gapful number since it is divisible by the number (87) formed by its first and last digit.

It is an amenable number.

81328557 is a deficient number, since it is larger than the sum of its proper divisors (30848883).

81328557 is a wasteful number, since it uses less digits than its factorization.

81328557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 934843.

The product of its digits is 67200, while the sum is 39.

The square root of 81328557 is about 9018.2346942182. The cubic root of 81328557 is about 433.2590956980.

The spelling of 81328557 in words is "eighty-one million, three hundred twenty-eight thousand, five hundred fifty-seven".