21427231 has 16 divisors (see below), whose sum is σ = 26613760. Its totient is φ = 16835040.

The previous prime is 21427223. The next prime is 21427247. The reversal of 21427231 is 13272412.

It is a cyclic number.

It is not a de Polignac number, because 21427231 - 2³ = 21427223 is a prime.

It is a super-2 number, since 2×21427231² = 918252456654722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21427271) 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, 1525 + ... + 6721.

It is an arithmetic number, because the mean of its divisors is an integer number (1663360).

Almost surely, 2^21427231 is an apocalyptic number.

21427231 is a deficient number, since it is larger than the sum of its proper divisors (5186529).

21427231 is a wasteful number, since it uses less digits than its factorization.

21427231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5254.

The product of its digits is 672, while the sum is 22.

The square root of 21427231 is about 4628.9557137653. The cubic root of 21427231 is about 277.7508204892.

Adding to 21427231 its reverse (13272412), we get a palindrome (34699643).

The spelling of 21427231 in words is "twenty-one million, four hundred twenty-seven thousand, two hundred thirty-one".