391644137 has 2 divisors, whose sum is σ = 391644138. Its totient is φ = 391644136.

The previous prime is 391644119. The next prime is 391644157. The reversal of 391644137 is 731446193.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 383024041 + 8620096 = 19571^2 + 2936^2 .

It is a cyclic number.

It is not a de Polignac number, because 391644137 - 2²² = 387449833 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 391644137.

It is not a weakly prime, because it can be changed into another prime (391644157) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195822068 + 195822069.

It is an arithmetic number, because the mean of its divisors is an integer number (195822069).

Almost surely, 2^391644137 is an apocalyptic number.

It is an amenable number.

391644137 is a deficient number, since it is larger than the sum of its proper divisors (1).

391644137 is an equidigital number, since it uses as much as digits as its factorization.

391644137 is an evil number, because the sum of its binary digits is even.

The product of its digits is 54432, while the sum is 38.

The square root of 391644137 is about 19790.0009348155. Note that the first 3 decimals coincide. The cubic root of 391644137 is about 731.6396104124.

The spelling of 391644137 in words is "three hundred ninety-one million, six hundred forty-four thousand, one hundred thirty-seven".