21077891 has 2 divisors, whose sum is σ = 21077892. Its totient is φ = 21077890.

The previous prime is 21077887. The next prime is 21077899. The reversal of 21077891 is 19877012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21077891 - 2² = 21077887 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21077899) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10538945 + 10538946.

It is an arithmetic number, because the mean of its divisors is an integer number (10538946).

Almost surely, 2^21077891 is an apocalyptic number.

21077891 is a deficient number, since it is larger than the sum of its proper divisors (1).

21077891 is an equidigital number, since it uses as much as digits as its factorization.

21077891 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7056, while the sum is 35.

The square root of 21077891 is about 4591.0664338474. The cubic root of 21077891 is about 276.2331005271.

The spelling of 21077891 in words is "twenty-one million, seventy-seven thousand, eight hundred ninety-one".