21291311 has 2 divisors, whose sum is σ = 21291312. Its totient is φ = 21291310.

The previous prime is 21291301. The next prime is 21291337. The reversal of 21291311 is 11319212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21291311 - 2⁶ = 21291247 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21291301) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10645655 + 10645656.

It is an arithmetic number, because the mean of its divisors is an integer number (10645656).

Almost surely, 2^21291311 is an apocalyptic number.

21291311 is a deficient number, since it is larger than the sum of its proper divisors (1).

21291311 is an equidigital number, since it uses as much as digits as its factorization.

21291311 is an evil number, because the sum of its binary digits is even.

The product of its digits is 108, while the sum is 20.

The square root of 21291311 is about 4614.2508601072. The cubic root of 21291311 is about 277.1622859237.

The spelling of 21291311 in words is "twenty-one million, two hundred ninety-one thousand, three hundred eleven".