21299321 has 2 divisors, whose sum is σ = 21299322. Its totient is φ = 21299320.

The previous prime is 21299303. The next prime is 21299329. The reversal of 21299321 is 12399212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20830096 + 469225 = 4564^2 + 685^2 .

It is a cyclic number.

It is not a de Polignac number, because 21299321 - 2²² = 17105017 is a prime.

It is a super-2 number, since 2×21299321² = 907322150122082, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21299329) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10649660 + 10649661.

It is an arithmetic number, because the mean of its divisors is an integer number (10649661).

Almost surely, 2^21299321 is an apocalyptic number.

It is an amenable number.

21299321 is a deficient number, since it is larger than the sum of its proper divisors (1).

21299321 is an equidigital number, since it uses as much as digits as its factorization.

21299321 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1944, while the sum is 29.

The square root of 21299321 is about 4615.1187417010. The cubic root of 21299321 is about 277.1970386226.

The spelling of 21299321 in words is "twenty-one million, two hundred ninety-nine thousand, three hundred twenty-one".