20421291 has 24 divisors (see below), whose sum is σ = 30279312. Its totient is φ = 12232000.

The previous prime is 20421287. The next prime is 20421329. The reversal of 20421291 is 19212402.

It is not a de Polignac number, because 20421291 - 2² = 20421287 is a prime.

It is a super-2 number, since 2×20421291² = 834058252213362, which contains 22 as substring.

It is a plaindrome in base 16.

It is not an unprimeable number, because it can be changed into a prime (20421241) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 36385 + ... + 36941.

It is an arithmetic number, because the mean of its divisors is an integer number (1261638).

Almost surely, 2^20421291 is an apocalyptic number.

20421291 is a deficient number, since it is larger than the sum of its proper divisors (9858021).

20421291 is a wasteful number, since it uses less digits than its factorization.

20421291 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 683 (or 672 counting only the distinct ones).

The product of its (nonzero) digits is 288, while the sum is 21.

The square root of 20421291 is about 4518.9922549170. The cubic root of 20421291 is about 273.3344664174.

Adding to 20421291 its reverse (19212402), we get a palindrome (39633693).

It can be divided in two parts, 2042 and 1291, that added together give a palindrome (3333).

The spelling of 20421291 in words is "twenty million, four hundred twenty-one thousand, two hundred ninety-one".