63991998 has 128 divisors (see below), whose sum is σ = 173015040. Its totient is φ = 17146080.

The previous prime is 63991997. The next prime is 63991999. The reversal of 63991998 is 89919936.

It is an interprime number because it is at equal distance from previous prime (63991997) and next prime (63991999).

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (63991997) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 503811 + ... + 503937.

It is an arithmetic number, because the mean of its divisors is an integer number (1351680).

Almost surely, 2^63991998 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 63991998, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (86507520).

63991998 is an abundant number, since it is smaller than the sum of its proper divisors (109023042).

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

63991998 is a wasteful number, since it uses less digits than its factorization.

63991998 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 219 (or 213 counting only the distinct ones).

The product of its digits is 944784, while the sum is 54.

The square root of 63991998 is about 7999.4998593662. The cubic root of 63991998 is about 399.9833284718.

It can be divided in two parts, 6 and 3991998, that added together give a square (3992004 = 1998²).

The spelling of 63991998 in words is "sixty-three million, nine hundred ninety-one thousand, nine hundred ninety-eight".