21172838 has 4 divisors (see below), whose sum is σ = 31759260. Its totient is φ = 10586418.

The previous prime is 21172829. The next prime is 21172849. The reversal of 21172838 is 83827112.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5293208 + ... + 5293211.

It is an arithmetic number, because the mean of its divisors is an integer number (7939815).

Almost surely, 2^21172838 is an apocalyptic number.

21172838 is a deficient number, since it is larger than the sum of its proper divisors (10586422).

21172838 is a wasteful number, since it uses less digits than its factorization.

21172838 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10586421.

The product of its digits is 5376, while the sum is 32.

The square root of 21172838 is about 4601.3952231905. The cubic root of 21172838 is about 276.6472504559.

The spelling of 21172838 in words is "twenty-one million, one hundred seventy-two thousand, eight hundred thirty-eight".