81388657 has 12 divisors (see below), whose sum is σ = 94870116. Its totient is φ = 69619200.

The previous prime is 81388633. The next prime is 81388669. The reversal of 81388657 is 75688318.

It can be written as a sum of positive squares in 2 ways, for example, as 45819361 + 35569296 = 6769^2 + 5964^2 .

It is not a de Polignac number, because 81388657 - 2¹¹ = 81386609 is a prime.

It is a super-2 number, since 2×81388657² = 13248226976527298, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81388687) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 27657 + ... + 30457.

It is an arithmetic number, because the mean of its divisors is an integer number (7905843).

Almost surely, 2^81388657 is an apocalyptic number.

It is an amenable number.

81388657 is a deficient number, since it is larger than the sum of its proper divisors (13481459).

81388657 is a wasteful number, since it uses less digits than its factorization.

81388657 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3408 (or 3401 counting only the distinct ones).

The product of its digits is 322560, while the sum is 46.

The square root of 81388657 is about 9021.5662165724. The cubic root of 81388657 is about 433.3657923746.

The spelling of 81388657 in words is "eighty-one million, three hundred eighty-eight thousand, six hundred fifty-seven".