21864229 has 2 divisors, whose sum is σ = 21864230. Its totient is φ = 21864228.

The previous prime is 21864217. The next prime is 21864239. The reversal of 21864229 is 92246812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 12852225 + 9012004 = 3585^2 + 3002^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21864229 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21864194 and 21864203.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21864209) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10932114 + 10932115.

It is an arithmetic number, because the mean of its divisors is an integer number (10932115).

Almost surely, 2^21864229 is an apocalyptic number.

It is an amenable number.

21864229 is a deficient number, since it is larger than the sum of its proper divisors (1).

21864229 is an equidigital number, since it uses as much as digits as its factorization.

21864229 is an evil number, because the sum of its binary digits is even.

The product of its digits is 13824, while the sum is 34.

The square root of 21864229 is about 4675.9201233554. The cubic root of 21864229 is about 279.6263255135.

The spelling of 21864229 in words is "twenty-one million, eight hundred sixty-four thousand, two hundred twenty-nine".