21534431 has 4 divisors (see below), whose sum is σ = 21570864. Its totient is φ = 21498000.

The previous prime is 21534421. The next prime is 21534437. The reversal of 21534431 is 13443512.

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 21534431 - 2¹⁴ = 21518047 is a prime.

It is a super-2 number, since 2×21534431² = 927463436987522, 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 = 21534397 and 21534406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21534437) 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, 17315 + ... + 18516.

It is an arithmetic number, because the mean of its divisors is an integer number (5392716).

Almost surely, 2^21534431 is an apocalyptic number.

21534431 is a deficient number, since it is larger than the sum of its proper divisors (36433).

21534431 is an equidigital number, since it uses as much as digits as its factorization.

21534431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36432.

The product of its digits is 1440, while the sum is 23.

The square root of 21534431 is about 4640.5205526966. The cubic root of 21534431 is about 278.2132440772.

Adding to 21534431 its reverse (13443512), we get a palindrome (34977943).

The spelling of 21534431 in words is "twenty-one million, five hundred thirty-four thousand, four hundred thirty-one".