391997623 has 2 divisors, whose sum is σ = 391997624. Its totient is φ = 391997622.

The previous prime is 391997609. The next prime is 391997633. The reversal of 391997623 is 326799193.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 391997623 - 2⁵ = 391997591 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (391997633) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195998811 + 195998812.

It is an arithmetic number, because the mean of its divisors is an integer number (195998812).

Almost surely, 2^391997623 is an apocalyptic number.

391997623 is a deficient number, since it is larger than the sum of its proper divisors (1).

391997623 is an equidigital number, since it uses as much as digits as its factorization.

391997623 is an evil number, because the sum of its binary digits is even.

The product of its digits is 551124, while the sum is 49.

The square root of 391997623 is about 19798.9298448174. The cubic root of 391997623 is about 731.8596627210.

The spelling of 391997623 in words is "three hundred ninety-one million, nine hundred ninety-seven thousand, six hundred twenty-three".