391916989 has 2 divisors, whose sum is σ = 391916990. Its totient is φ = 391916988.

The previous prime is 391916983. The next prime is 391917013. The reversal of 391916989 is 989619193.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 283652964 + 108264025 = 16842^2 + 10405^2 .

It is an emirp because it is prime and its reverse (989619193) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 391916989 - 2³ = 391916981 is a prime.

It is a super-2 number, since 2×391916989² = 307197852533652242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (391916981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195958494 + 195958495.

It is an arithmetic number, because the mean of its divisors is an integer number (195958495).

Almost surely, 2^391916989 is an apocalyptic number.

It is an amenable number.

391916989 is a deficient number, since it is larger than the sum of its proper divisors (1).

391916989 is an equidigital number, since it uses as much as digits as its factorization.

391916989 is an evil number, because the sum of its binary digits is even.

The product of its digits is 944784, while the sum is 55.

The square root of 391916989 is about 19796.8934179078. The cubic root of 391916989 is about 731.8094780470.

The spelling of 391916989 in words is "three hundred ninety-one million, nine hundred sixteen thousand, nine hundred eighty-nine".