21088231 has 4 divisors (see below), whose sum is σ = 21149352. Its totient is φ = 21027112.

The previous prime is 21088219. The next prime is 21088237. The reversal of 21088231 is 13288012.

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-21088231 is a prime.

It is a super-2 number, since 2×21088231² = 889426973418722, 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 = 21088196 and 21088205.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21088237) 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, 30040 + ... + 30733.

It is an arithmetic number, because the mean of its divisors is an integer number (5287338).

Almost surely, 2^21088231 is an apocalyptic number.

21088231 is a deficient number, since it is larger than the sum of its proper divisors (61121).

21088231 is an equidigital number, since it uses as much as digits as its factorization.

21088231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61120.

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 21088231 is about 4592.1923957953. The cubic root of 21088231 is about 276.2782629096.

The spelling of 21088231 in words is "twenty-one million, eighty-eight thousand, two hundred thirty-one".