21030791 has 2 divisors, whose sum is σ = 21030792. Its totient is φ = 21030790.

The previous prime is 21030781. The next prime is 21030797. The reversal of 21030791 is 19703012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21030791 - 2¹⁴ = 21014407 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21030797) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10515395 + 10515396.

It is an arithmetic number, because the mean of its divisors is an integer number (10515396).

Almost surely, 2^21030791 is an apocalyptic number.

21030791 is a deficient number, since it is larger than the sum of its proper divisors (1).

21030791 is an equidigital number, since it uses as much as digits as its factorization.

21030791 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 378, while the sum is 23.

The square root of 21030791 is about 4585.9340379033. The cubic root of 21030791 is about 276.0271931129.

The spelling of 21030791 in words is "twenty-one million, thirty thousand, seven hundred ninety-one".