72815661 has 6 divisors (see below), whose sum is σ = 105178190. Its totient is φ = 48543768.

The previous prime is 72815653. The next prime is 72815671. The reversal of 72815661 is 16651827.

It can be written as a sum of positive squares in only one way, i.e., 46498761 + 26316900 = 6819^2 + 5130^2 .

It is not a de Polignac number, because 72815661 - 2³ = 72815653 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72815671) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 4045306 + ... + 4045323.

Almost surely, 2^72815661 is an apocalyptic number.

It is an amenable number.

72815661 is a deficient number, since it is larger than the sum of its proper divisors (32362529).

72815661 is a wasteful number, since it uses less digits than its factorization.

72815661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8090635 (or 8090632 counting only the distinct ones).

The product of its digits is 20160, while the sum is 36.

The square root of 72815661 is about 8533.2093024840. The cubic root of 72815661 is about 417.5818353452.

The spelling of 72815661 in words is "seventy-two million, eight hundred fifteen thousand, six hundred sixty-one".