63990821 has 2 divisors, whose sum is σ = 63990822. Its totient is φ = 63990820.

The previous prime is 63990799. The next prime is 63990827. The reversal of 63990821 is 12809936.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 56776225 + 7214596 = 7535^2 + 2686^2 .

It is a cyclic number.

It is not a de Polignac number, because 63990821 - 2⁶ = 63990757 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (63990827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 31995410 + 31995411.

It is an arithmetic number, because the mean of its divisors is an integer number (31995411).

Almost surely, 2^63990821 is an apocalyptic number.

It is an amenable number.

63990821 is a deficient number, since it is larger than the sum of its proper divisors (1).

63990821 is an equidigital number, since it uses as much as digits as its factorization.

63990821 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 38.

The square root of 63990821 is about 7999.4262919287. The cubic root of 63990821 is about 399.9808761690.

The spelling of 63990821 in words is "sixty-three million, nine hundred ninety thousand, eight hundred twenty-one".