21655171 has 2 divisors, whose sum is σ = 21655172. Its totient is φ = 21655170.

The previous prime is 21655147. The next prime is 21655189. The reversal of 21655171 is 17155612.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21655171 - 2⁷ = 21655043 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21655871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10827585 + 10827586.

It is an arithmetic number, because the mean of its divisors is an integer number (10827586).

Almost surely, 2^21655171 is an apocalyptic number.

21655171 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655171 is an equidigital number, since it uses as much as digits as its factorization.

21655171 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2100, while the sum is 28.

The square root of 21655171 is about 4653.5116847387. The cubic root of 21655171 is about 278.7322405518.

The spelling of 21655171 in words is "twenty-one million, six hundred fifty-five thousand, one hundred seventy-one".