21128194 has 4 divisors (see below), whose sum is σ = 31692294. Its totient is φ = 10564096.

The previous prime is 21128189. The next prime is 21128197. The reversal of 21128194 is 49182112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 18020025 + 3108169 = 4245^2 + 1763^2 .

It is not an unprimeable number, because it can be changed into a prime (21128197) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5282047 + ... + 5282050.

Almost surely, 2^21128194 is an apocalyptic number.

21128194 is a deficient number, since it is larger than the sum of its proper divisors (10564100).

21128194 is a wasteful number, since it uses less digits than its factorization.

21128194 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10564099.

The product of its digits is 1152, while the sum is 28.

The square root of 21128194 is about 4596.5415259736. The cubic root of 21128194 is about 276.4526720582.

The spelling of 21128194 in words is "twenty-one million, one hundred twenty-eight thousand, one hundred ninety-four".