20490391 has 2 divisors, whose sum is σ = 20490392. Its totient is φ = 20490390.

The previous prime is 20490373. The next prime is 20490397. The reversal of 20490391 is 19309402.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20490391 - 2²³ = 12101783 is a prime.

It is a super-2 number, since 2×20490391² = 839712246665762, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20490397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10245195 + 10245196.

It is an arithmetic number, because the mean of its divisors is an integer number (10245196).

Almost surely, 2^20490391 is an apocalyptic number.

20490391 is a deficient number, since it is larger than the sum of its proper divisors (1).

20490391 is an equidigital number, since it uses as much as digits as its factorization.

20490391 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1944, while the sum is 28.

The square root of 20490391 is about 4526.6313081584. The cubic root of 20490391 is about 273.6424154158.

Adding to 20490391 its reverse (19309402), we get a palindrome (39799793).

The spelling of 20490391 in words is "twenty million, four hundred ninety thousand, three hundred ninety-one".