63999621 has 24 divisors (see below), whose sum is σ = 105940224. Its totient is φ = 36470880.

The previous prime is 63999599. The next prime is 63999641. The reversal of 63999621 is 12699936.

It is a happy number.

63999621 is a `hidden beast` number, since 639 + 9 + 9 + 6 + 2 + 1 = 666.

It is not a de Polignac number, because 63999621 - 2⁷ = 63999493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (63999641) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 25975 + ... + 28331.

It is an arithmetic number, because the mean of its divisors is an integer number (4414176).

Almost surely, 2^63999621 is an apocalyptic number.

It is an amenable number.

63999621 is a deficient number, since it is larger than the sum of its proper divisors (41940603).

63999621 is a wasteful number, since it uses less digits than its factorization.

63999621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2801 (or 2798 counting only the distinct ones).

The product of its digits is 157464, while the sum is 45.

The square root of 63999621 is about 7999.9763124649. The cubic root of 63999621 is about 399.9992104151. Note that the first 3 decimals are identical.

It can be divided in two parts, 63999 and 621, that added together give a triangular number (64620 = T₃₅₉).

The spelling of 63999621 in words is "sixty-three million, nine hundred ninety-nine thousand, six hundred twenty-one".