21284431 has 4 divisors (see below), whose sum is σ = 24325072. Its totient is φ = 18243792.

The previous prime is 21284423. The next prime is 21284489. The reversal of 21284431 is 13448212.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21284431 - 2³ = 21284423 is a prime.

It is a super-2 number, since 2×21284431² = 906054005987522, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21284396 and 21284405.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21284401) 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, 1520310 + ... + 1520323.

It is an arithmetic number, because the mean of its divisors is an integer number (6081268).

Almost surely, 2^21284431 is an apocalyptic number.

21284431 is a deficient number, since it is larger than the sum of its proper divisors (3040641).

21284431 is an equidigital number, since it uses as much as digits as its factorization.

21284431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3040640.

The product of its digits is 1536, while the sum is 25.

The square root of 21284431 is about 4613.5052834044. The cubic root of 21284431 is about 277.1324289559.

The spelling of 21284431 in words is "twenty-one million, two hundred eighty-four thousand, four hundred thirty-one".