65978721 has 12 divisors (see below), whose sum is σ = 96286372. Its totient is φ = 43531776.

The previous prime is 65978707. The next prime is 65978723. The reversal of 65978721 is 12787956.

It can be written as a sum of positive squares in 2 ways, for example, as 21902400 + 44076321 = 4680^2 + 6639^2 .

It is not a de Polignac number, because 65978721 - 2⁶ = 65978657 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (65978723) 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, 36916 + ... + 38661.

Almost surely, 2^65978721 is an apocalyptic number.

It is an amenable number.

65978721 is a deficient number, since it is larger than the sum of its proper divisors (30307651).

65978721 is a wasteful number, since it uses less digits than its factorization.

65978721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75680 (or 75677 counting only the distinct ones).

The product of its digits is 211680, while the sum is 45.

The square root of 65978721 is about 8122.7286671414. The cubic root of 65978721 is about 404.0805663098.

The spelling of 65978721 in words is "sixty-five million, nine hundred seventy-eight thousand, seven hundred twenty-one".