21716539 has 4 divisors (see below), whose sum is σ = 23387056. Its totient is φ = 20046024.

The previous prime is 21716533. The next prime is 21716567. The reversal of 21716539 is 93561712.

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

It is a cyclic number.

It is not a de Polignac number, because 21716539 - 2⁵ = 21716507 is a prime.

It is a super-2 number, since 2×21716539² = 943216132277042, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21716533) 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, 835239 + ... + 835264.

It is an arithmetic number, because the mean of its divisors is an integer number (5846764).

Almost surely, 2^21716539 is an apocalyptic number.

21716539 is a deficient number, since it is larger than the sum of its proper divisors (1670517).

21716539 is a wasteful number, since it uses less digits than its factorization.

21716539 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1670516.

The product of its digits is 11340, while the sum is 34.

The square root of 21716539 is about 4660.1007499838. The cubic root of 21716539 is about 278.9952894637.

The spelling of 21716539 in words is "twenty-one million, seven hundred sixteen thousand, five hundred thirty-nine".