63991999 has 2 divisors, whose sum is σ = 63992000. Its totient is φ = 63991998.

The previous prime is 63991997. The next prime is 63992017. The reversal of 63991999 is 99919936.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 63991999 - 2¹ = 63991997 is a prime.

Together with 63991997, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (63991997) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 31995999 + 31996000.

It is an arithmetic number, because the mean of its divisors is an integer number (31996000).

Almost surely, 2^63991999 is an apocalyptic number.

63991999 is a deficient number, since it is larger than the sum of its proper divisors (1).

63991999 is an equidigital number, since it uses as much as digits as its factorization.

63991999 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1062882, while the sum is 55.

The square root of 63991999 is about 7999.4999218701. The cubic root of 63991999 is about 399.9833305553.

The spelling of 63991999 in words is "sixty-three million, nine hundred ninety-one thousand, nine hundred ninety-nine".