21716837 has 4 divisors (see below), whose sum is σ = 22994316. Its totient is φ = 20439360.

The previous prime is 21716831. The next prime is 21716857. The reversal of 21716837 is 73861712.

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 15952036 + 5764801 = 3994^2 + 2401^2 .

It is a cyclic number.

It is not a de Polignac number, because 21716837 - 2²⁰ = 20668261 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21716797 and 21716806.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21716831) 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, 638714 + ... + 638747.

It is an arithmetic number, because the mean of its divisors is an integer number (5748579).

Almost surely, 2^21716837 is an apocalyptic number.

It is an amenable number.

21716837 is a deficient number, since it is larger than the sum of its proper divisors (1277479).

21716837 is a wasteful number, since it uses less digits than its factorization.

21716837 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1277478.

The product of its digits is 14112, while the sum is 35.

The square root of 21716837 is about 4660.1327234318. The cubic root of 21716837 is about 278.9965656065.

The spelling of 21716837 in words is "twenty-one million, seven hundred sixteen thousand, eight hundred thirty-seven".