63999990 has 64 divisors (see below), whose sum is σ = 171460800. Its totient is φ = 16987392.

The previous prime is 63999979. The next prime is 64000031. The reversal of 63999990 is 9999936.

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 78706 + ... + 79514.

It is an arithmetic number, because the mean of its divisors is an integer number (2679075).

Almost surely, 2^63999990 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 63999990, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (85730400).

63999990 is an abundant number, since it is smaller than the sum of its proper divisors (107460810).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

63999990 is a wasteful number, since it uses less digits than its factorization.

63999990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1118 (or 1112 counting only the distinct ones).

The product of its (nonzero) digits is 1062882, while the sum is 54.

The square root of 63999990 is about 7999.9993750000. Note that the first 3 decimals coincide. The cubic root of 63999990 is about 399.9999791667. Note that the first 4 decimals are identical.

Subtracting from 63999990 its sum of digits (54), we obtain a palindrome (63999936).

The spelling of 63999990 in words is "sixty-three million, nine hundred ninety-nine thousand, nine hundred ninety".