21718871 has 2 divisors, whose sum is σ = 21718872. Its totient is φ = 21718870.

The previous prime is 21718849. The next prime is 21718891. The reversal of 21718871 is 17881712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21718871 - 2¹⁸ = 21456727 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21718891) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10859435 + 10859436.

It is an arithmetic number, because the mean of its divisors is an integer number (10859436).

Almost surely, 2^21718871 is an apocalyptic number.

21718871 is a deficient number, since it is larger than the sum of its proper divisors (1).

21718871 is an equidigital number, since it uses as much as digits as its factorization.

21718871 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6272, while the sum is 35.

The square root of 21718871 is about 4660.3509524498. The cubic root of 21718871 is about 279.0052756118.

The spelling of 21718871 in words is "twenty-one million, seven hundred eighteen thousand, eight hundred seventy-one".