21155938 has 4 divisors (see below), whose sum is σ = 31733910. Its totient is φ = 10577968.

The previous prime is 21155921. The next prime is 21155977. The reversal of 21155938 is 83955112.

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., 17247409 + 3908529 = 4153^2 + 1977^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5288983 + ... + 5288986.

Almost surely, 2^21155938 is an apocalyptic number.

21155938 is a deficient number, since it is larger than the sum of its proper divisors (10577972).

21155938 is a wasteful number, since it uses less digits than its factorization.

21155938 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10577971.

The product of its digits is 10800, while the sum is 34.

The square root of 21155938 is about 4599.5584570695. The cubic root of 21155938 is about 276.5736249454.

The spelling of 21155938 in words is "twenty-one million, one hundred fifty-five thousand, nine hundred thirty-eight".