21638307 has 4 divisors (see below), whose sum is σ = 28851080. Its totient is φ = 14425536.

The previous prime is 21638273. The next prime is 21638311. The reversal of 21638307 is 70383612.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21638307 - 2¹¹ = 21636259 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 (21638317) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3606382 + ... + 3606387.

It is an arithmetic number, because the mean of its divisors is an integer number (7212770).

Almost surely, 2^21638307 is an apocalyptic number.

21638307 is a deficient number, since it is larger than the sum of its proper divisors (7212773).

21638307 is an equidigital number, since it uses as much as digits as its factorization.

21638307 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7212772.

The product of its (nonzero) digits is 6048, while the sum is 30.

The square root of 21638307 is about 4651.6993668981. The cubic root of 21638307 is about 278.6598673649.

It can be divided in two parts, 21638 and 307, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21638307 in words is "twenty-one million, six hundred thirty-eight thousand, three hundred seven".