21836321 has 6 divisors (see below), whose sum is σ = 23645430. Its totient is φ = 20156448.

The previous prime is 21836273. The next prime is 21836323. The reversal of 21836321 is 12363812.

It can be written as a sum of positive squares in 3 ways, for example, as 2131600 + 19704721 = 1460^2 + 4439^2 .

It is not a de Polignac number, because 21836321 - 2²² = 17642017 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21836323) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 64436 + ... + 64773.

It is an arithmetic number, because the mean of its divisors is an integer number (3940905).

Almost surely, 2^21836321 is an apocalyptic number.

It is an amenable number.

21836321 is a deficient number, since it is larger than the sum of its proper divisors (1809109).

21836321 is a wasteful number, since it uses less digits than its factorization.

21836321 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 129235 (or 129222 counting only the distinct ones).

The product of its digits is 1728, while the sum is 26.

The square root of 21836321 is about 4672.9349449784. The cubic root of 21836321 is about 279.5073010532.

The spelling of 21836321 in words is "twenty-one million, eight hundred thirty-six thousand, three hundred twenty-one".