21638378 has 8 divisors (see below), whose sum is σ = 34165920. Its totient is φ = 10249740.

The previous prime is 21638371. The next prime is 21638381. The reversal of 21638378 is 87383612.

It is a happy number.

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

It is a Harshad number since it is a multiple of its sum of digits (38), and also a Moran number because the ratio is a prime number: 569431 = 21638378 / (2 + 1 + 6 + 3 + 8 + 3 + 7 + 8).

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (21638371) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 284678 + ... + 284753.

It is an arithmetic number, because the mean of its divisors is an integer number (4270740).

Almost surely, 2^21638378 is an apocalyptic number.

21638378 is a deficient number, since it is larger than the sum of its proper divisors (12527542).

21638378 is a wasteful number, since it uses less digits than its factorization.

21638378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 569452.

The product of its digits is 48384, while the sum is 38.

The square root of 21638378 is about 4651.7069985114. The cubic root of 21638378 is about 278.6601721458.

The spelling of 21638378 in words is "twenty-one million, six hundred thirty-eight thousand, three hundred seventy-eight".