21117937 has 4 divisors (see below), whose sum is σ = 21240180. Its totient is φ = 20995696.

The previous prime is 21117881. The next prime is 21117953. The reversal of 21117937 is 73971112.

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

It can be written as a sum of positive squares in 2 ways, for example, as 8755681 + 12362256 = 2959^2 + 3516^2 .

It is a cyclic number.

It is not a de Polignac number, because 21117937 - 2¹⁹ = 20593649 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21117899 and 21117908.

It is not an unprimeable number, because it can be changed into a prime (21117997) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 60862 + ... + 61207.

It is an arithmetic number, because the mean of its divisors is an integer number (5310045).

Almost surely, 2^21117937 is an apocalyptic number.

It is an amenable number.

21117937 is a deficient number, since it is larger than the sum of its proper divisors (122243).

21117937 is a wasteful number, since it uses less digits than its factorization.

21117937 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 122242.

The product of its digits is 2646, while the sum is 31.

The square root of 21117937 is about 4595.4256603714. The cubic root of 21117937 is about 276.4079287792.

The spelling of 21117937 in words is "twenty-one million, one hundred seventeen thousand, nine hundred thirty-seven".