21732251 has 4 divisors (see below), whose sum is σ = 21781752. Its totient is φ = 21682752.

The previous prime is 21732247. The next prime is 21732253. The reversal of 21732251 is 15223712.

It is a happy number.

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 21732251 - 2² = 21732247 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21732253) 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, 24086 + ... + 24971.

It is an arithmetic number, because the mean of its divisors is an integer number (5445438).

Almost surely, 2^21732251 is an apocalyptic number.

21732251 is a deficient number, since it is larger than the sum of its proper divisors (49501).

21732251 is an equidigital number, since it uses as much as digits as its factorization.

21732251 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 49500.

The product of its digits is 840, while the sum is 23.

The square root of 21732251 is about 4661.7862456359. The cubic root of 21732251 is about 279.0625579671.

Adding to 21732251 its reverse (15223712), we get a palindrome (36955963).

The spelling of 21732251 in words is "twenty-one million, seven hundred thirty-two thousand, two hundred fifty-one".