21171911 has 2 divisors, whose sum is σ = 21171912. Its totient is φ = 21171910.

The previous prime is 21171883. The next prime is 21171929. The reversal of 21171911 is 11917112.

It is a happy number.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21171911 - 2¹⁰ = 21170887 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21171961) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10585955 + 10585956.

It is an arithmetic number, because the mean of its divisors is an integer number (10585956).

Almost surely, 2^21171911 is an apocalyptic number.

21171911 is a deficient number, since it is larger than the sum of its proper divisors (1).

21171911 is an equidigital number, since it uses as much as digits as its factorization.

21171911 is an evil number, because the sum of its binary digits is even.

The product of its digits is 126, while the sum is 23.

The square root of 21171911 is about 4601.2944917708. The cubic root of 21171911 is about 276.6432129600.

The spelling of 21171911 in words is "twenty-one million, one hundred seventy-one thousand, nine hundred eleven".