21819569 has 2 divisors, whose sum is σ = 21819570. Its totient is φ = 21819568.

The previous prime is 21819541. The next prime is 21819587. The reversal of 21819569 is 96591812.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21669025 + 150544 = 4655^2 + 388^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21819569 is a prime.

It is a super-2 number, since 2×21819569² = 952187182691522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21819599) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10909784 + 10909785.

It is an arithmetic number, because the mean of its divisors is an integer number (10909785).

Almost surely, 2^21819569 is an apocalyptic number.

It is an amenable number.

21819569 is a deficient number, since it is larger than the sum of its proper divisors (1).

21819569 is an equidigital number, since it uses as much as digits as its factorization.

21819569 is an evil number, because the sum of its binary digits is even.

The product of its digits is 38880, while the sum is 41.

The square root of 21819569 is about 4671.1421515514. The cubic root of 21819569 is about 279.4358069558.

The spelling of 21819569 in words is "twenty-one million, eight hundred nineteen thousand, five hundred sixty-nine".