391018421 has 2 divisors, whose sum is σ = 391018422. Its totient is φ = 391018420.

The previous prime is 391018417. The next prime is 391018477. The reversal of 391018421 is 124810193.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 300502225 + 90516196 = 17335^2 + 9514^2 .

It is a cyclic number.

It is not a de Polignac number, because 391018421 - 2² = 391018417 is a prime.

It is a super-2 number, since 2×391018421² = 305790811122666482, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (391018721) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 195509210 + 195509211.

It is an arithmetic number, because the mean of its divisors is an integer number (195509211).

Almost surely, 2^391018421 is an apocalyptic number.

It is an amenable number.

391018421 is a deficient number, since it is larger than the sum of its proper divisors (1).

391018421 is an equidigital number, since it uses as much as digits as its factorization.

391018421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 29.

The square root of 391018421 is about 19774.1857228054. The cubic root of 391018421 is about 731.2497644726.

The spelling of 391018421 in words is "three hundred ninety-one million, eighteen thousand, four hundred twenty-one".