21245131 has 4 divisors (see below), whose sum is σ = 21267000. Its totient is φ = 21223264.

The previous prime is 21245129. The next prime is 21245153. The reversal of 21245131 is 13154212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21245131 - 2¹ = 21245129 is a prime.

It is a super-2 number, since 2×21245131² = 902711182414322, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21245099 and 21245108.

It is not an unprimeable number, because it can be changed into a prime (21245111) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 9406 + ... + 11443.

It is an arithmetic number, because the mean of its divisors is an integer number (5316750).

Almost surely, 2^21245131 is an apocalyptic number.

21245131 is a deficient number, since it is larger than the sum of its proper divisors (21869).

21245131 is a wasteful number, since it uses less digits than its factorization.

21245131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21868.

The product of its digits is 240, while the sum is 19.

The square root of 21245131 is about 4609.2440811916. The cubic root of 21245131 is about 276.9617562445.

Adding to 21245131 its reverse (13154212), we get a palindrome (34399343).

The spelling of 21245131 in words is "twenty-one million, two hundred forty-five thousand, one hundred thirty-one".