21233431 has 4 divisors (see below), whose sum is σ = 22351000. Its totient is φ = 20115864.

The previous prime is 21233413. The next prime is 21233441. The reversal of 21233431 is 13433212.

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 21233431 - 2⁹ = 21232919 is a prime.

It is a super-2 number, since 2×21233431² = 901717184063522, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (19), and also a Moran number because the ratio is a prime number: 1117549 = 21233431 / (2 + 1 + 2 + 3 + 3 + 4 + 3 + 1).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21233399 and 21233408.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21233411) 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, 558756 + ... + 558793.

It is an arithmetic number, because the mean of its divisors is an integer number (5587750).

Almost surely, 2^21233431 is an apocalyptic number.

21233431 is a deficient number, since it is larger than the sum of its proper divisors (1117569).

21233431 is a wasteful number, since it uses less digits than its factorization.

21233431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1117568.

The product of its digits is 432, while the sum is 19.

The square root of 21233431 is about 4607.9747178126. The cubic root of 21233431 is about 276.9109046308.

Adding to 21233431 its reverse (13433212), we get a palindrome (34666643).

The spelling of 21233431 in words is "twenty-one million, two hundred thirty-three thousand, four hundred thirty-one".