21211431 has 4 divisors (see below), whose sum is σ = 28281912. Its totient is φ = 14140952.

The previous prime is 21211403. The next prime is 21211433. The reversal of 21211431 is 13411212.

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 21211431 - 2⁶ = 21211367 is a prime.

It is a super-2 number, since 2×21211431² = 899849610135522, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21211431.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21211433) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3535236 + ... + 3535241.

It is an arithmetic number, because the mean of its divisors is an integer number (7070478).

Almost surely, 2^21211431 is an apocalyptic number.

21211431 is a deficient number, since it is larger than the sum of its proper divisors (7070481).

21211431 is an equidigital number, since it uses as much as digits as its factorization.

21211431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7070480.

The product of its digits is 48, while the sum is 15.

The square root of 21211431 is about 4605.5869332801. The cubic root of 21211431 is about 276.8152356029.

Adding to 21211431 its reverse (13411212), we get a palindrome (34622643).

The spelling of 21211431 in words is "twenty-one million, two hundred eleven thousand, four hundred thirty-one".