21793921 has 2 divisors, whose sum is σ = 21793922. Its totient is φ = 21793920.

The previous prime is 21793909. The next prime is 21793927. The reversal of 21793921 is 12939712.

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., 11296321 + 10497600 = 3361^2 + 3240^2 .

It is a cyclic number.

It is not a de Polignac number, because 21793921 - 2¹¹ = 21791873 is a prime.

It is not a weakly prime, because it can be changed into another prime (21793927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10896960 + 10896961.

It is an arithmetic number, because the mean of its divisors is an integer number (10896961).

Almost surely, 2^21793921 is an apocalyptic number.

It is an amenable number.

21793921 is a deficient number, since it is larger than the sum of its proper divisors (1).

21793921 is an equidigital number, since it uses as much as digits as its factorization.

21793921 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6804, while the sum is 34.

The square root of 21793921 is about 4668.3959772067. The cubic root of 21793921 is about 279.3262756207.

The spelling of 21793921 in words is "twenty-one million, seven hundred ninety-three thousand, nine hundred twenty-one".