63971721 has 16 divisors (see below), whose sum is σ = 103389120. Its totient is φ = 38770560.

The previous prime is 63971701. The next prime is 63971723. The reversal of 63971721 is 12717936.

It is a happy number.

63971721 is a `hidden beast` number, since 639 + 7 + 17 + 2 + 1 = 666.

It is not a de Polignac number, because 63971721 - 2⁶ = 63971657 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (63971723) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 107400 + ... + 107993.

It is an arithmetic number, because the mean of its divisors is an integer number (6461820).

Almost surely, 2^63971721 is an apocalyptic number.

It is an amenable number.

63971721 is a deficient number, since it is larger than the sum of its proper divisors (39417399).

63971721 is a wasteful number, since it uses less digits than its factorization.

63971721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215413 (or 215407 counting only the distinct ones).

The product of its digits is 15876, while the sum is 36.

The square root of 63971721 is about 7998.2323672171. The cubic root of 63971721 is about 399.9410767372.

It can be divided in two parts, 6397 and 1721, that added together give a palindrome (8118).

The spelling of 63971721 in words is "sixty-three million, nine hundred seventy-one thousand, seven hundred twenty-one".