63911991 has 32 divisors (see below), whose sum is σ = 105396480. Its totient is φ = 33868800.

The previous prime is 63911983. The next prime is 63912019. The reversal of 63911991 is 19911936.

It is a happy number.

It is not a de Polignac number, because 63911991 - 2³ = 63911983 is a prime.

It is a Smith number, since the sum of its digits (39) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (63911921) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 4231 + ... + 12071.

It is an arithmetic number, because the mean of its divisors is an integer number (3293640).

Almost surely, 2^63911991 is an apocalyptic number.

63911991 is a deficient number, since it is larger than the sum of its proper divisors (41484489).

63911991 is a wasteful number, since it uses less digits than its factorization.

63911991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7887.

The product of its digits is 13122, while the sum is 39.

The square root of 63911991 is about 7994.4975451869. The cubic root of 63911991 is about 399.8165638074.

The spelling of 63911991 in words is "sixty-three million, nine hundred eleven thousand, nine hundred ninety-one".