21426431 has 4 divisors (see below), whose sum is σ = 23074632. Its totient is φ = 19778232.

The previous prime is 21426421. The next prime is 21426437. The reversal of 21426431 is 13462412.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21426431 is a prime.

It is a super-2 number, since 2×21426431² = 918183890795522, 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 = 21426397 and 21426406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21426437) 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, 824081 + ... + 824106.

It is an arithmetic number, because the mean of its divisors is an integer number (5768658).

Almost surely, 2^21426431 is an apocalyptic number.

21426431 is a deficient number, since it is larger than the sum of its proper divisors (1648201).

21426431 is a wasteful number, since it uses less digits than its factorization.

21426431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1648200.

The product of its digits is 1152, while the sum is 23.

The square root of 21426431 is about 4628.8693003800. The cubic root of 21426431 is about 277.7473637753.

Adding to 21426431 its reverse (13462412), we get a palindrome (34888843).

The spelling of 21426431 in words is "twenty-one million, four hundred twenty-six thousand, four hundred thirty-one".