21638845 has 8 divisors (see below), whose sum is σ = 26005464. Its totient is φ = 17285184.

The previous prime is 21638833. The next prime is 21638867. The reversal of 21638845 is 54883612.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 3644281 + 17994564 = 1909^2 + 4242^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21638845 - 2¹⁹ = 21114557 is a prime.

It is a super-2 number, since 2×21638845² = 936479225868050, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 927 + ... + 6643.

It is an arithmetic number, because the mean of its divisors is an integer number (3250683).

Almost surely, 2^21638845 is an apocalyptic number.

It is an amenable number.

21638845 is a deficient number, since it is larger than the sum of its proper divisors (4366619).

21638845 is an equidigital number, since it uses as much as digits as its factorization.

21638845 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6479.

The product of its digits is 46080, while the sum is 37.

The square root of 21638845 is about 4651.7571948673. The cubic root of 21638845 is about 278.6621768149.

The spelling of 21638845 in words is "twenty-one million, six hundred thirty-eight thousand, eight hundred forty-five".