21432531 has 8 divisors (see below), whose sum is σ = 28604880. Its totient is φ = 14274272.

The previous prime is 21432493. The next prime is 21432539. The reversal of 21432531 is 13523412.

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

It is a cyclic number.

It is not a de Polignac number, because 21432531 - 2⁷ = 21432403 is a prime.

It is a super-2 number, since 2×21432531² = 918706770131922, which contains 22 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21432498 and 21432507.

It is not an unprimeable number, because it can be changed into a prime (21432539) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 781 + ... + 6593.

It is an arithmetic number, because the mean of its divisors is an integer number (3575610).

Almost surely, 2^21432531 is an apocalyptic number.

21432531 is a deficient number, since it is larger than the sum of its proper divisors (7172349).

21432531 is a wasteful number, since it uses less digits than its factorization.

21432531 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7045.

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

The square root of 21432531 is about 4629.5281617029. The cubic root of 21432531 is about 277.7737190459.

Adding to 21432531 its reverse (13523412), we get a palindrome (34955943).

The spelling of 21432531 in words is "twenty-one million, four hundred thirty-two thousand, five hundred thirty-one".