21641897 has 2 divisors, whose sum is σ = 21641898. Its totient is φ = 21641896.

The previous prime is 21641887. The next prime is 21641903. The reversal of 21641897 is 79814612.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20830096 + 811801 = 4564^2 + 901^2 .

It is a cyclic number.

It is not a de Polignac number, because 21641897 - 2²⁴ = 4864681 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21641897.

It is not a weakly prime, because it can be changed into another prime (21641887) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10820948 + 10820949.

It is an arithmetic number, because the mean of its divisors is an integer number (10820949).

Almost surely, 2^21641897 is an apocalyptic number.

It is an amenable number.

21641897 is a deficient number, since it is larger than the sum of its proper divisors (1).

21641897 is an equidigital number, since it uses as much as digits as its factorization.

21641897 is an evil number, because the sum of its binary digits is even.

The product of its digits is 24192, while the sum is 38.

The square root of 21641897 is about 4652.0852313774. The cubic root of 21641897 is about 278.6752772828.

The spelling of 21641897 in words is "twenty-one million, six hundred forty-one thousand, eight hundred ninety-seven".