21051231 has 8 divisors (see below), whose sum is σ = 28358064. Its totient is φ = 13889280.

The previous prime is 21051203. The next prime is 21051241. The reversal of 21051231 is 13215012.

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

It is not a de Polignac number, because 21051231 - 2⁷ = 21051103 is a prime.

It is a super-2 number, since 2×21051231² = 886308653230722, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21051231.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21051241) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 35880 + ... + 36461.

It is an arithmetic number, because the mean of its divisors is an integer number (3544758).

Almost surely, 2^21051231 is an apocalyptic number.

21051231 is a deficient number, since it is larger than the sum of its proper divisors (7306833).

21051231 is an equidigital number, since it uses as much as digits as its factorization.

21051231 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72441.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21051231 is about 4588.1620503204. The cubic root of 21051231 is about 276.1165885297.

Adding to 21051231 its reverse (13215012), we get a palindrome (34266243).

The spelling of 21051231 in words is "twenty-one million, fifty-one thousand, two hundred thirty-one".