691919939 has 2 divisors, whose sum is σ = 691919940. Its totient is φ = 691919938.

The previous prime is 691919897. The next prime is 691919957. The reversal of 691919939 is 939919196.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-691919939 is a prime.

It is not a weakly prime, because it can be changed into another prime (691919959) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 345959969 + 345959970.

It is an arithmetic number, because the mean of its divisors is an integer number (345959970).

Almost surely, 2^691919939 is an apocalyptic number.

691919939 is a deficient number, since it is larger than the sum of its proper divisors (1).

691919939 is an equidigital number, since it uses as much as digits as its factorization.

691919939 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1062882, while the sum is 56.

The square root of 691919939 is about 26304.3711006365. The cubic root of 691919939 is about 884.4744297702.

The spelling of 691919939 in words is "six hundred ninety-one million, nine hundred nineteen thousand, nine hundred thirty-nine".