21865229 has 2 divisors, whose sum is σ = 21865230. Its totient is φ = 21865228.

The previous prime is 21865211. The next prime is 21865237. The reversal of 21865229 is 92256812.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21855625 + 9604 = 4675^2 + 98^2 .

It is a cyclic number.

It is not a de Polignac number, because 21865229 - 2¹⁶ = 21799693 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21865279) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10932614 + 10932615.

It is an arithmetic number, because the mean of its divisors is an integer number (10932615).

Almost surely, 2^21865229 is an apocalyptic number.

It is an amenable number.

21865229 is a deficient number, since it is larger than the sum of its proper divisors (1).

21865229 is an equidigital number, since it uses as much as digits as its factorization.

21865229 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17280, while the sum is 35.

The square root of 21865229 is about 4676.0270529585. The cubic root of 21865229 is about 279.6305885202.

The spelling of 21865229 in words is "twenty-one million, eight hundred sixty-five thousand, two hundred twenty-nine".