21722851 has 2 divisors, whose sum is σ = 21722852. Its totient is φ = 21722850.

The previous prime is 21722837. The next prime is 21722861. The reversal of 21722851 is 15822712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21722851 - 2¹⁵ = 21690083 is a prime.

It is not a weakly prime, because it can be changed into another prime (21722801) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10861425 + 10861426.

It is an arithmetic number, because the mean of its divisors is an integer number (10861426).

Almost surely, 2^21722851 is an apocalyptic number.

21722851 is a deficient number, since it is larger than the sum of its proper divisors (1).

21722851 is an equidigital number, since it uses as much as digits as its factorization.

21722851 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21722851 is about 4660.7779393573. Note that the first 3 decimals coincide. The cubic root of 21722851 is about 279.0223172155.

The spelling of 21722851 in words is "twenty-one million, seven hundred twenty-two thousand, eight hundred fifty-one".