21228737 has 2 divisors, whose sum is σ = 21228738. Its totient is φ = 21228736.

The previous prime is 21228709. The next prime is 21228761. The reversal of 21228737 is 73782212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21169201 + 59536 = 4601^2 + 244^2 .

It is a cyclic number.

It is not a de Polignac number, because 21228737 - 2¹⁴ = 21212353 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21228797) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10614368 + 10614369.

It is an arithmetic number, because the mean of its divisors is an integer number (10614369).

Almost surely, 2^21228737 is an apocalyptic number.

It is an amenable number.

21228737 is a deficient number, since it is larger than the sum of its proper divisors (1).

21228737 is an equidigital number, since it uses as much as digits as its factorization.

21228737 is an evil number, because the sum of its binary digits is even.

The product of its digits is 9408, while the sum is 32.

The square root of 21228737 is about 4607.4653552686. The cubic root of 21228737 is about 276.8904978866.

The spelling of 21228737 in words is "twenty-one million, two hundred twenty-eight thousand, seven hundred thirty-seven".