21112251 has 4 divisors (see below), whose sum is σ = 28149672. Its totient is φ = 14074832.

The previous prime is 21112241. The next prime is 21112279. The reversal of 21112251 is 15221112.

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 21112251 - 2¹³ = 21104059 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21112251.

It is not an unprimeable number, because it can be changed into a prime (21112241) 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, 3518706 + ... + 3518711.

It is an arithmetic number, because the mean of its divisors is an integer number (7037418).

Almost surely, 2^21112251 is an apocalyptic number.

21112251 is a deficient number, since it is larger than the sum of its proper divisors (7037421).

21112251 is an equidigital number, since it uses as much as digits as its factorization.

21112251 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7037420.

The product of its digits is 40, while the sum is 15.

The square root of 21112251 is about 4594.8069600365. The cubic root of 21112251 is about 276.3831189605.

Adding to 21112251 its reverse (15221112), we get a palindrome (36333363).

The spelling of 21112251 in words is "twenty-one million, one hundred twelve thousand, two hundred fifty-one".