21907397 has 2 divisors, whose sum is σ = 21907398. Its totient is φ = 21907396.

The previous prime is 21907387. The next prime is 21907429. The reversal of 21907397 is 79370912.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18395521 + 3511876 = 4289^2 + 1874^2 .

It is a cyclic number.

It is not a de Polignac number, because 21907397 - 2¹⁶ = 21841861 is a prime.

It is a Chen prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21907397.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21907307) 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, 10953698 + 10953699.

It is an arithmetic number, because the mean of its divisors is an integer number (10953699).

Almost surely, 2^21907397 is an apocalyptic number.

It is an amenable number.

21907397 is a deficient number, since it is larger than the sum of its proper divisors (1).

21907397 is an equidigital number, since it uses as much as digits as its factorization.

21907397 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 23814, while the sum is 38.

The square root of 21907397 is about 4680.5338370746. The cubic root of 21907397 is about 279.8102328108.

The spelling of 21907397 in words is "twenty-one million, nine hundred seven thousand, three hundred ninety-seven".