63721521 has 6 divisors (see below), whose sum is σ = 92042210. Its totient is φ = 42481008.

The previous prime is 63721517. The next prime is 63721543. The reversal of 63721521 is 12512736.

It is a happy number.

63721521 is a `hidden beast` number, since 637 + 2 + 1 + 5 + 21 = 666.

It can be written as a sum of positive squares in only one way, i.e., 32080896 + 31640625 = 5664^2 + 5625^2 .

It is not a de Polignac number, because 63721521 - 2² = 63721517 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (63721501) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 3540076 + ... + 3540093.

Almost surely, 2^63721521 is an apocalyptic number.

It is an amenable number.

63721521 is a deficient number, since it is larger than the sum of its proper divisors (28320689).

63721521 is a wasteful number, since it uses less digits than its factorization.

63721521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7080175 (or 7080172 counting only the distinct ones).

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

The square root of 63721521 is about 7982.5760879556. The cubic root of 63721521 is about 399.4189918992.

The spelling of 63721521 in words is "sixty-three million, seven hundred twenty-one thousand, five hundred twenty-one".