21298021 has 2 divisors, whose sum is σ = 21298022. Its totient is φ = 21298020.

The previous prime is 21298001. The next prime is 21298033. The reversal of 21298021 is 12089212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21288996 + 9025 = 4614^2 + 95^2 .

It is a cyclic number.

It is not a de Polignac number, because 21298021 - 2⁹ = 21297509 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21298001) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10649010 + 10649011.

It is an arithmetic number, because the mean of its divisors is an integer number (10649011).

Almost surely, 2^21298021 is an apocalyptic number.

It is an amenable number.

21298021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21298021 is an equidigital number, since it uses as much as digits as its factorization.

21298021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 25.

The square root of 21298021 is about 4614.9778981053. The cubic root of 21298021 is about 277.1913989517.

The spelling of 21298021 in words is "twenty-one million, two hundred ninety-eight thousand, twenty-one".