21431253 has 8 divisors (see below), whose sum is σ = 28837600. Its totient is φ = 14156208.

The previous prime is 21431231. The next prime is 21431269. The reversal of 21431253 is 35213412.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21431253 - 2¹⁰ = 21430229 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21431353) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 32443 + ... + 33096.

It is an arithmetic number, because the mean of its divisors is an integer number (3604700).

Almost surely, 2^21431253 is an apocalyptic number.

It is an amenable number.

21431253 is a deficient number, since it is larger than the sum of its proper divisors (7406347).

21431253 is a wasteful number, since it uses less digits than its factorization.

21431253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 65651.

The product of its digits is 720, while the sum is 21.

The square root of 21431253 is about 4629.3901326201. The cubic root of 21431253 is about 277.7681978148.

Adding to 21431253 its reverse (35213412), we get a palindrome (56644665).

The spelling of 21431253 in words is "twenty-one million, four hundred thirty-one thousand, two hundred fifty-three".