391405381 has 2 divisors, whose sum is σ = 391405382. Its totient is φ = 391405380.

The previous prime is 391405361. The next prime is 391405387. The reversal of 391405381 is 183504193.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 381577156 + 9828225 = 19534^2 + 3135^2 .

It is a cyclic number.

It is not a de Polignac number, because 391405381 - 2¹³ = 391397189 is a prime.

It is a super-2 number, since 2×391405381² = 306396344551510322, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (391405387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195702690 + 195702691.

It is an arithmetic number, because the mean of its divisors is an integer number (195702691).

Almost surely, 2^391405381 is an apocalyptic number.

It is an amenable number.

391405381 is a deficient number, since it is larger than the sum of its proper divisors (1).

391405381 is an equidigital number, since it uses as much as digits as its factorization.

391405381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 391405381 is about 19783.9677769653. The cubic root of 391405381 is about 731.4909049598.

It can be divided in two parts, 39140 and 5381, that added together give a square (44521 = 211²).

The spelling of 391405381 in words is "three hundred ninety-one million, four hundred five thousand, three hundred eighty-one".