21648638 has 32 divisors (see below), whose sum is σ = 37895040. Its totient is φ = 9171360.

The previous prime is 21648631. The next prime is 21648647. The reversal of 21648638 is 83684612.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (38).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21648631) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 27620 + ... + 28392.

It is an arithmetic number, because the mean of its divisors is an integer number (1184220).

Almost surely, 2^21648638 is an apocalyptic number.

21648638 is a deficient number, since it is larger than the sum of its proper divisors (16246402).

21648638 is a wasteful number, since it uses less digits than its factorization.

21648638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 872.

The product of its digits is 55296, while the sum is 38.

The square root of 21648638 is about 4652.8096887795. The cubic root of 21648638 is about 278.7042081267.

The spelling of 21648638 in words is "twenty-one million, six hundred forty-eight thousand, six hundred thirty-eight".