21873251 has 2 divisors, whose sum is σ = 21873252. Its totient is φ = 21873250.

The previous prime is 21873233. The next prime is 21873277. The reversal of 21873251 is 15237812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21873251 - 2¹⁴ = 21856867 is a prime.

It is not a weakly prime, because it can be changed into another prime (21873451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10936625 + 10936626.

It is an arithmetic number, because the mean of its divisors is an integer number (10936626).

Almost surely, 2^21873251 is an apocalyptic number.

21873251 is a deficient number, since it is larger than the sum of its proper divisors (1).

21873251 is an equidigital number, since it uses as much as digits as its factorization.

21873251 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3360, while the sum is 29.

The square root of 21873251 is about 4676.8847537651. The cubic root of 21873251 is about 279.6647816571.

The spelling of 21873251 in words is "twenty-one million, eight hundred seventy-three thousand, two hundred fifty-one".