21819197 has 2 divisors, whose sum is σ = 21819198. Its totient is φ = 21819196.

The previous prime is 21819173. The next prime is 21819209. The reversal of 21819197 is 79191812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16556761 + 5262436 = 4069^2 + 2294^2 .

It is a cyclic number.

It is not a de Polignac number, because 21819197 - 2⁸ = 21818941 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 21819197.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21819137) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10909598 + 10909599.

It is an arithmetic number, because the mean of its divisors is an integer number (10909599).

Almost surely, 2^21819197 is an apocalyptic number.

It is an amenable number.

21819197 is a deficient number, since it is larger than the sum of its proper divisors (1).

21819197 is an equidigital number, since it uses as much as digits as its factorization.

21819197 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9072, while the sum is 38.

The square root of 21819197 is about 4671.1023324265. The cubic root of 21819197 is about 279.4342189209.

The spelling of 21819197 in words is "twenty-one million, eight hundred nineteen thousand, one hundred ninety-seven".