21431273 has 4 divisors (see below), whose sum is σ = 21441168. Its totient is φ = 21421380.

The previous prime is 21431269. The next prime is 21431303. The reversal of 21431273 is 37213412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21431273 - 2² = 21431269 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21431173) 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, 143 + ... + 6548.

It is an arithmetic number, because the mean of its divisors is an integer number (5360292).

Almost surely, 2^21431273 is an apocalyptic number.

It is an amenable number.

21431273 is a deficient number, since it is larger than the sum of its proper divisors (9895).

21431273 is an equidigital number, since it uses as much as digits as its factorization.

21431273 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9894.

The product of its digits is 1008, while the sum is 23.

The square root of 21431273 is about 4629.3922927313. The cubic root of 21431273 is about 277.7682842207.

Adding to 21431273 its reverse (37213412), we get a palindrome (58644685).

The spelling of 21431273 in words is "twenty-one million, four hundred thirty-one thousand, two hundred seventy-three".