391993649 has 2 divisors, whose sum is σ = 391993650. Its totient is φ = 391993648.

The previous prime is 391993639. The next prime is 391993681. The reversal of 391993649 is 946399193.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 333318049 + 58675600 = 18257^2 + 7660^2 .

It is a cyclic number.

It is not a de Polignac number, because 391993649 - 2²⁴ = 375216433 is a prime.

It is a super-4 number, since 4×391993649⁴ (a number of 35 digits) contains 4444 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 391993649.

It is not a weakly prime, because it can be changed into another prime (391993639) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195996824 + 195996825.

It is an arithmetic number, because the mean of its divisors is an integer number (195996825).

Almost surely, 2^391993649 is an apocalyptic number.

It is an amenable number.

391993649 is a deficient number, since it is larger than the sum of its proper divisors (1).

391993649 is an equidigital number, since it uses as much as digits as its factorization.

391993649 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1417176, while the sum is 53.

The square root of 391993649 is about 19798.8294856034. The cubic root of 391993649 is about 731.8571895597.

The spelling of 391993649 in words is "three hundred ninety-one million, nine hundred ninety-three thousand, six hundred forty-nine".