21918037 has 2 divisors, whose sum is σ = 21918038. Its totient is φ = 21918036.

The previous prime is 21918019. The next prime is 21918053. The reversal of 21918037 is 73081912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15163236 + 6754801 = 3894^2 + 2599^2 .

It is a cyclic number.

It is not a de Polignac number, because 21918037 - 2²³ = 13529429 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21918007) 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, 10959018 + 10959019.

It is an arithmetic number, because the mean of its divisors is an integer number (10959019).

Almost surely, 2^21918037 is an apocalyptic number.

It is an amenable number.

21918037 is a deficient number, since it is larger than the sum of its proper divisors (1).

21918037 is an equidigital number, since it uses as much as digits as its factorization.

21918037 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3024, while the sum is 31.

The square root of 21918037 is about 4681.6703215840. The cubic root of 21918037 is about 279.8555249561.

Adding to 21918037 its reverse (73081912), we get a palindrome (94999949).

The spelling of 21918037 in words is "twenty-one million, nine hundred eighteen thousand, thirty-seven".