21065837 has 4 divisors (see below), whose sum is σ = 22686300. Its totient is φ = 19445376.

The previous prime is 21065831. The next prime is 21065843. The reversal of 21065837 is 73856012.

It is a happy number.

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

It is an interprime number because it is at equal distance from previous prime (21065831) and next prime (21065843).

It can be written as a sum of positive squares in 2 ways, for example, as 4206601 + 16859236 = 2051^2 + 4106^2 .

It is a cyclic number.

It is not a de Polignac number, because 21065837 - 2²⁴ = 4288621 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21065831) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 810212 + ... + 810237.

It is an arithmetic number, because the mean of its divisors is an integer number (5671575).

Almost surely, 2^21065837 is an apocalyptic number.

It is an amenable number.

21065837 is a deficient number, since it is larger than the sum of its proper divisors (1620463).

21065837 is a wasteful number, since it uses less digits than its factorization.

21065837 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1620462.

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 21065837 is about 4589.7534792187. The cubic root of 21065837 is about 276.1804331970.

The spelling of 21065837 in words is "twenty-one million, sixty-five thousand, eight hundred thirty-seven".