21538378 has 8 divisors (see below), whose sum is σ = 32330340. Its totient is φ = 10761600.

The previous prime is 21538339. The next prime is 21538379. The reversal of 21538378 is 87383512.

It can be written as a sum of positive squares in 2 ways, for example, as 20820969 + 717409 = 4563^2 + 847^2 .

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

It is not an unprimeable number, because it can be changed into a prime (21538379) 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, 928 + ... + 6628.

Almost surely, 2^21538378 is an apocalyptic number.

21538378 is a deficient number, since it is larger than the sum of its proper divisors (10791962).

21538378 is a wasteful number, since it uses less digits than its factorization.

21538378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7592.

The product of its digits is 40320, while the sum is 37.

The square root of 21538378 is about 4640.9458087765. The cubic root of 21538378 is about 278.2302407432.

The spelling of 21538378 in words is "twenty-one million, five hundred thirty-eight thousand, three hundred seventy-eight".