20402491 has 2 divisors, whose sum is σ = 20402492. Its totient is φ = 20402490.

The previous prime is 20402467. The next prime is 20402497. The reversal of 20402491 is 19420402.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20402491 - 2¹³ = 20394299 is a prime.

It is not a weakly prime, because it can be changed into another prime (20402497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10201245 + 10201246.

It is an arithmetic number, because the mean of its divisors is an integer number (10201246).

Almost surely, 2^20402491 is an apocalyptic number.

20402491 is a deficient number, since it is larger than the sum of its proper divisors (1).

20402491 is an equidigital number, since it uses as much as digits as its factorization.

20402491 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 20402491 is about 4516.9116661719. The cubic root of 20402491 is about 273.2505627164.

Adding to 20402491 its reverse (19420402), we get a palindrome (39822893).

The spelling of 20402491 in words is "twenty million, four hundred two thousand, four hundred ninety-one".