21228951 has 4 divisors (see below), whose sum is σ = 28305272. Its totient is φ = 14152632.

The previous prime is 21228901. The next prime is 21228953. The reversal of 21228951 is 15982212.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21228951 - 2¹¹ = 21226903 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21228953) 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, 3538156 + ... + 3538161.

It is an arithmetic number, because the mean of its divisors is an integer number (7076318).

Almost surely, 2^21228951 is an apocalyptic number.

21228951 is a deficient number, since it is larger than the sum of its proper divisors (7076321).

21228951 is an equidigital number, since it uses as much as digits as its factorization.

21228951 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7076320.

The product of its digits is 2880, while the sum is 30.

The square root of 21228951 is about 4607.4885783906. The cubic root of 21228951 is about 276.8914282979.

The spelling of 21228951 in words is "twenty-one million, two hundred twenty-eight thousand, nine hundred fifty-one".