21219901 has 2 divisors, whose sum is σ = 21219902. Its totient is φ = 21219900.

The previous prime is 21219883. The next prime is 21219917. The reversal of 21219901 is 10991212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19131876 + 2088025 = 4374^2 + 1445^2 .

It is a cyclic number.

It is not a de Polignac number, because 21219901 - 2¹³ = 21211709 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21219001) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10609950 + 10609951.

It is an arithmetic number, because the mean of its divisors is an integer number (10609951).

Almost surely, 2^21219901 is an apocalyptic number.

It is an amenable number.

21219901 is a deficient number, since it is larger than the sum of its proper divisors (1).

21219901 is an equidigital number, since it uses as much as digits as its factorization.

21219901 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 25.

The square root of 21219901 is about 4606.5063768544. The cubic root of 21219901 is about 276.8520760065.

The spelling of 21219901 in words is "twenty-one million, two hundred nineteen thousand, nine hundred one".