81657497 has 4 divisors (see below), whose sum is σ = 85955280. Its totient is φ = 77359716.

The previous prime is 81657491. The next prime is 81657509. The reversal of 81657497 is 79475618.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 81657497 - 2¹⁰ = 81656473 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81657491) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2148863 + ... + 2148900.

It is an arithmetic number, because the mean of its divisors is an integer number (21488820).

Almost surely, 2^81657497 is an apocalyptic number.

It is an amenable number.

81657497 is a deficient number, since it is larger than the sum of its proper divisors (4297783).

81657497 is a wasteful number, since it uses less digits than its factorization.

81657497 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4297782.

The product of its digits is 423360, while the sum is 47.

The square root of 81657497 is about 9036.4537845330. The cubic root of 81657497 is about 433.8424272412.

The spelling of 81657497 in words is "eighty-one million, six hundred fifty-seven thousand, four hundred ninety-seven".