21266891 has 2 divisors, whose sum is σ = 21266892. Its totient is φ = 21266890.

The previous prime is 21266887. The next prime is 21266911. The reversal of 21266891 is 19866212.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21266891 - 2² = 21266887 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21266291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10633445 + 10633446.

It is an arithmetic number, because the mean of its divisors is an integer number (10633446).

Almost surely, 2^21266891 is an apocalyptic number.

21266891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21266891 is an equidigital number, since it uses as much as digits as its factorization.

21266891 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10368, while the sum is 35.

The square root of 21266891 is about 4611.6039509047. The cubic root of 21266891 is about 277.0562819251.

The spelling of 21266891 in words is "twenty-one million, two hundred sixty-six thousand, eight hundred ninety-one".