501399991 has 2 divisors, whose sum is σ = 501399992. Its totient is φ = 501399990.

The previous prime is 501399973. The next prime is 501400007. The reversal of 501399991 is 199993105.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-501399991 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (501399791) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 250699995 + 250699996.

It is an arithmetic number, because the mean of its divisors is an integer number (250699996).

Almost surely, 2^501399991 is an apocalyptic number.

501399991 is a deficient number, since it is larger than the sum of its proper divisors (1).

501399991 is an equidigital number, since it uses as much as digits as its factorization.

501399991 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 98415, while the sum is 46.

The square root of 501399991 is about 22391.9626428770. The cubic root of 501399991 is about 794.4406180605.

It can be divided in two parts, 50 and 1399991, that added together give a palindrome (1400041).

The spelling of 501399991 in words is "five hundred one million, three hundred ninety-nine thousand, nine hundred ninety-one".