21621293 has 2 divisors, whose sum is σ = 21621294. Its totient is φ = 21621292.

The previous prime is 21621289. The next prime is 21621329. The reversal of 21621293 is 39212612.

Together with next prime (21621329) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20912329 + 708964 = 4573^2 + 842^2 .

It is a cyclic number.

It is not a de Polignac number, because 21621293 - 2² = 21621289 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21621233) 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, 10810646 + 10810647.

It is an arithmetic number, because the mean of its divisors is an integer number (10810647).

Almost surely, 2^21621293 is an apocalyptic number.

It is an amenable number.

21621293 is a deficient number, since it is larger than the sum of its proper divisors (1).

21621293 is an equidigital number, since it uses as much as digits as its factorization.

21621293 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1296, while the sum is 26.

The square root of 21621293 is about 4649.8702132425. The cubic root of 21621293 is about 278.5868123247.

The spelling of 21621293 in words is "twenty-one million, six hundred twenty-one thousand, two hundred ninety-three".