21698213 has 2 divisors, whose sum is σ = 21698214. Its totient is φ = 21698212.

The previous prime is 21698207. The next prime is 21698267. The reversal of 21698213 is 31289612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 15856324 + 5841889 = 3982^2 + 2417^2 .

It is a cyclic number.

It is not a de Polignac number, because 21698213 - 2⁸ = 21697957 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21698213.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21698203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10849106 + 10849107.

It is an arithmetic number, because the mean of its divisors is an integer number (10849107).

Almost surely, 2^21698213 is an apocalyptic number.

It is an amenable number.

21698213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21698213 is an equidigital number, since it uses as much as digits as its factorization.

21698213 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5184, while the sum is 32.

The square root of 21698213 is about 4658.1340684871. The cubic root of 21698213 is about 278.9167885179.

The spelling of 21698213 in words is "twenty-one million, six hundred ninety-eight thousand, two hundred thirteen".