21872251 has 8 divisors (see below), whose sum is σ = 23698224. Its totient is φ = 20106240.

The previous prime is 21872237. The next prime is 21872269. The reversal of 21872251 is 15227812.

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

It is not a de Polignac number, because 21872251 - 2⁹ = 21871739 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21872231) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 14230 + ... + 15691.

It is an arithmetic number, because the mean of its divisors is an integer number (2962278).

Almost surely, 2^21872251 is an apocalyptic number.

21872251 is a deficient number, since it is larger than the sum of its proper divisors (1825973).

21872251 is a wasteful number, since it uses less digits than its factorization.

21872251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 29981.

The product of its digits is 2240, while the sum is 28.

The square root of 21872251 is about 4676.7778437724. Note that the first 3 decimals coincide. The cubic root of 21872251 is about 279.6605196928.

The spelling of 21872251 in words is "twenty-one million, eight hundred seventy-two thousand, two hundred fifty-one".