21788138 has 8 divisors (see below), whose sum is σ = 33479460. Its totient is φ = 10628320.

The previous prime is 21788113. The next prime is 21788147. The reversal of 21788138 is 83188712.

It can be written as a sum of positive squares in 2 ways, for example, as 21687649 + 100489 = 4657^2 + 317^2 .

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

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 132773 + ... + 132936.

Almost surely, 2^21788138 is an apocalyptic number.

21788138 is a deficient number, since it is larger than the sum of its proper divisors (11691322).

21788138 is a wasteful number, since it uses less digits than its factorization.

21788138 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 265752.

The product of its digits is 21504, while the sum is 38.

The square root of 21788138 is about 4667.7765584912. The cubic root of 21788138 is about 279.3015670984.

The spelling of 21788138 in words is "twenty-one million, seven hundred eighty-eight thousand, one hundred thirty-eight".