63951991 has 2 divisors, whose sum is σ = 63951992. Its totient is φ = 63951990.

The previous prime is 63951971. The next prime is 63952013. The reversal of 63951991 is 19915936.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 63951991 - 2¹⁷ = 63820919 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (63951961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 31975995 + 31975996.

It is an arithmetic number, because the mean of its divisors is an integer number (31975996).

Almost surely, 2^63951991 is an apocalyptic number.

63951991 is a deficient number, since it is larger than the sum of its proper divisors (1).

63951991 is an equidigital number, since it uses as much as digits as its factorization.

63951991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 65610, while the sum is 43.

The square root of 63951991 is about 7996.9988745779. The cubic root of 63951991 is about 399.8999562302.

The spelling of 63951991 in words is "sixty-three million, nine hundred fifty-one thousand, nine hundred ninety-one".