21388194 has 12 divisors (see below), whose sum is σ = 46341126. Its totient is φ = 7129392.

The previous prime is 21388189. The next prime is 21388201. The reversal of 21388194 is 49188312.

It can be written as a sum of positive squares in only one way, i.e., 12006225 + 9381969 = 3465^2 + 3063^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 594099 + ... + 594134.

Almost surely, 2^21388194 is an apocalyptic number.

21388194 is an abundant number, since it is smaller than the sum of its proper divisors (24952932).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21388194 is a wasteful number, since it uses less digits than its factorization.

21388194 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1188241 (or 1188238 counting only the distinct ones).

The product of its digits is 13824, while the sum is 36.

The square root of 21388194 is about 4624.7371817218. The cubic root of 21388194 is about 277.5820453774.

The spelling of 21388194 in words is "twenty-one million, three hundred eighty-eight thousand, one hundred ninety-four".