63720521 has 4 divisors (see below), whose sum is σ = 63795732. Its totient is φ = 63645312.

The previous prime is 63720493. The next prime is 63720581. The reversal of 63720521 is 12502736.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 53860921 + 9859600 = 7339^2 + 3140^2 .

It is a cyclic number.

It is not a de Polignac number, because 63720521 - 2⁶ = 63720457 is a prime.

It is a super-2 number, since 2×63720521² = 8120609593022882, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (63720581) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 36320 + ... + 38033.

It is an arithmetic number, because the mean of its divisors is an integer number (15948933).

Almost surely, 2^63720521 is an apocalyptic number.

It is an amenable number.

63720521 is a deficient number, since it is larger than the sum of its proper divisors (75211).

63720521 is an equidigital number, since it uses as much as digits as its factorization.

63720521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75210.

The product of its (nonzero) digits is 2520, while the sum is 26.

The square root of 63720521 is about 7982.5134512884. The cubic root of 63720521 is about 399.4169024896.

The spelling of 63720521 in words is "sixty-three million, seven hundred twenty thousand, five hundred twenty-one".