21051937 has 4 divisors (see below), whose sum is σ = 21062020. Its totient is φ = 21041856.

The previous prime is 21051913. The next prime is 21051949. The reversal of 21051937 is 73915012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 15335056 + 5716881 = 3916^2 + 2391^2 .

It is a cyclic number.

It is not a de Polignac number, because 21051937 - 2⁷ = 21051809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21051907) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 612 + ... + 6517.

It is an arithmetic number, because the mean of its divisors is an integer number (5265505).

Almost surely, 2^21051937 is an apocalyptic number.

It is an amenable number.

21051937 is a deficient number, since it is larger than the sum of its proper divisors (10083).

21051937 is an equidigital number, since it uses as much as digits as its factorization.

21051937 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10082.

The product of its (nonzero) digits is 1890, while the sum is 28.

The square root of 21051937 is about 4588.2389868009. The cubic root of 21051937 is about 276.1196752238.

Adding to 21051937 its reverse (73915012), we get a palindrome (94966949).

The spelling of 21051937 in words is "twenty-one million, fifty-one thousand, nine hundred thirty-seven".