21864213 has 12 divisors (see below), whose sum is σ = 36093408. Its totient is φ = 12493800.

The previous prime is 21864209. The next prime is 21864217. The reversal of 21864213 is 31246812.

21864213 is a `hidden beast` number, since 2 + 1 + 8 + 642 + 13 = 666.

It is an interprime number because it is at equal distance from previous prime (21864209) and next prime (21864217).

It is not a de Polignac number, because 21864213 - 2² = 21864209 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21864217) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 173463 + ... + 173588.

It is an arithmetic number, because the mean of its divisors is an integer number (3007784).

Almost surely, 2^21864213 is an apocalyptic number.

It is an amenable number.

21864213 is a deficient number, since it is larger than the sum of its proper divisors (14229195).

21864213 is a wasteful number, since it uses less digits than its factorization.

21864213 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 347064 (or 347061 counting only the distinct ones).

The product of its digits is 2304, while the sum is 27.

The square root of 21864213 is about 4675.9184124619. The cubic root of 21864213 is about 279.6262573043.

The spelling of 21864213 in words is "twenty-one million, eight hundred sixty-four thousand, two hundred thirteen".