72005661 has 36 divisors (see below), whose sum is σ = 128732448. Its totient is φ = 37975392.

The previous prime is 72005603. The next prime is 72005683. The reversal of 72005661 is 16650027.

It is a de Polignac number, because none of the positive numbers 2^k-72005661 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (72005161) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 7266 + ... + 14028.

Almost surely, 2^72005661 is an apocalyptic number.

It is an amenable number.

72005661 is a deficient number, since it is larger than the sum of its proper divisors (56726787).

72005661 is a wasteful number, since it uses less digits than its factorization.

72005661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6802 (or 6786 counting only the distinct ones).

The product of its (nonzero) digits is 2520, while the sum is 27.

The square root of 72005661 is about 8485.6149453060. The cubic root of 72005661 is about 416.0276674307.

Adding to 72005661 its reverse (16650027), we get a palindrome (88655688).

The spelling of 72005661 in words is "seventy-two million, five thousand, six hundred sixty-one".