21027791 has 2 divisors, whose sum is σ = 21027792. Its totient is φ = 21027790.

The previous prime is 21027767. The next prime is 21027833. The reversal of 21027791 is 19772012.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21027791 is a prime.

It is a Sophie Germain prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21027701) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10513895 + 10513896.

It is an arithmetic number, because the mean of its divisors is an integer number (10513896).

Almost surely, 2^21027791 is an apocalyptic number.

21027791 is a deficient number, since it is larger than the sum of its proper divisors (1).

21027791 is an equidigital number, since it uses as much as digits as its factorization.

21027791 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1764, while the sum is 29.

The square root of 21027791 is about 4585.6069391085. The cubic root of 21027791 is about 276.0140675809.

The spelling of 21027791 in words is "twenty-one million, twenty-seven thousand, seven hundred ninety-one".