21219641 has 2 divisors, whose sum is σ = 21219642. Its totient is φ = 21219640.

The previous prime is 21219631. The next prime is 21219703. The reversal of 21219641 is 14691212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16362025 + 4857616 = 4045^2 + 2204^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21219641 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21219641.

It is not a weakly prime, because it can be changed into another prime (21219631) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10609820 + 10609821.

It is an arithmetic number, because the mean of its divisors is an integer number (10609821).

Almost surely, 2^21219641 is an apocalyptic number.

It is an amenable number.

21219641 is a deficient number, since it is larger than the sum of its proper divisors (1).

21219641 is an equidigital number, since it uses as much as digits as its factorization.

21219641 is an evil number, because the sum of its binary digits is even.

The product of its digits is 864, while the sum is 26.

The square root of 21219641 is about 4606.4781558149. The cubic root of 21219641 is about 276.8509452781.

The spelling of 21219641 in words is "twenty-one million, two hundred nineteen thousand, six hundred forty-one".