21029231 has 4 divisors (see below), whose sum is σ = 21061152. Its totient is φ = 20997312.

The previous prime is 21029207. The next prime is 21029237. The reversal of 21029231 is 13292012.

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 21029231 - 2⁶ = 21029167 is a prime.

It is a super-2 number, since 2×21029231² = 884457112902722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21029237) 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, 14951 + ... + 16296.

It is an arithmetic number, because the mean of its divisors is an integer number (5265288).

Almost surely, 2^21029231 is an apocalyptic number.

21029231 is a deficient number, since it is larger than the sum of its proper divisors (31921).

21029231 is an equidigital number, since it uses as much as digits as its factorization.

21029231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31920.

The product of its (nonzero) digits is 216, while the sum is 20.

The square root of 21029231 is about 4585.7639494418. The cubic root of 21029231 is about 276.0203679921.

The spelling of 21029231 in words is "twenty-one million, twenty-nine thousand, two hundred thirty-one".