21804971 has 2 divisors, whose sum is σ = 21804972. Its totient is φ = 21804970.

The previous prime is 21804961. The next prime is 21804983. The reversal of 21804971 is 17940812.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21804971 - 2¹⁴ = 21788587 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21804901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10902485 + 10902486.

It is an arithmetic number, because the mean of its divisors is an integer number (10902486).

Almost surely, 2^21804971 is an apocalyptic number.

21804971 is a deficient number, since it is larger than the sum of its proper divisors (1).

21804971 is an equidigital number, since it uses as much as digits as its factorization.

21804971 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4032, while the sum is 32.

The square root of 21804971 is about 4669.5793172405. The cubic root of 21804971 is about 279.3734758445.

The spelling of 21804971 in words is "twenty-one million, eight hundred four thousand, nine hundred seventy-one".