21189708634 has 4 divisors (see below), whose sum is σ = 31784562954. Its totient is φ = 10594854316.

The previous prime is 21189708623. The next prime is 21189708641. The reversal of 21189708634 is 43680798112.

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., 12260025625 + 8929683009 = 110725^2 + 94497^2 .

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5297427157 + ... + 5297427160.

Almost surely, 2^21189708634 is an apocalyptic number.

21189708634 is a deficient number, since it is larger than the sum of its proper divisors (10594854320).

21189708634 is a wasteful number, since it uses less digits than its factorization.

21189708634 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10594854319.

The product of its (nonzero) digits is 580608, while the sum is 49.

The spelling of 21189708634 in words is "twenty-one billion, one hundred eighty-nine million, seven hundred eight thousand, six hundred thirty-four".