21221431 has 16 divisors (see below), whose sum is σ = 26611200. Its totient is φ = 16440480.

The previous prime is 21221429. The next prime is 21221441. The reversal of 21221431 is 13412212.

It is not a de Polignac number, because 21221431 - 2¹ = 21221429 is a prime.

It is a super-2 number, since 2×21221431² = 900698267375522, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21221411) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 14470 + ... + 15868.

It is an arithmetic number, because the mean of its divisors is an integer number (1663200).

Almost surely, 2^21221431 is an apocalyptic number.

21221431 is a deficient number, since it is larger than the sum of its proper divisors (5389769).

21221431 is a wasteful number, since it uses less digits than its factorization.

21221431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1614.

The product of its digits is 96, while the sum is 16.

The square root of 21221431 is about 4606.6724433152. The cubic root of 21221431 is about 276.8587297211.

Adding to 21221431 its reverse (13412212), we get a palindrome (34633643).

It can be divided in two parts, 2122 and 1431, that added together give a palindrome (3553).

The spelling of 21221431 in words is "twenty-one million, two hundred twenty-one thousand, four hundred thirty-one".