21432731 has 4 divisors (see below), whose sum is σ = 22012032. Its totient is φ = 20853432.

The previous prime is 21432701. The next prime is 21432737. The reversal of 21432731 is 13723412.

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 21432731 - 2¹⁸ = 21170587 is a prime.

It is a super-2 number, since 2×21432731² = 918723916236722, 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 = 21432697 and 21432706.

It is not an unprimeable number, because it can be changed into a prime (21432737) 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, 289595 + ... + 289668.

It is an arithmetic number, because the mean of its divisors is an integer number (5503008).

Almost surely, 2^21432731 is an apocalyptic number.

21432731 is a deficient number, since it is larger than the sum of its proper divisors (579301).

21432731 is an equidigital number, since it uses as much as digits as its factorization.

21432731 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 579300.

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

The square root of 21432731 is about 4629.5497621259. The cubic root of 21432731 is about 277.7745830684.

The spelling of 21432731 in words is "twenty-one million, four hundred thirty-two thousand, seven hundred thirty-one".