21161817 has 40 divisors (see below), whose sum is σ = 33988416. Its totient is φ = 13087008.

The previous prime is 21161783. The next prime is 21161857. The reversal of 21161817 is 71816112.

It is not a de Polignac number, because 21161817 - 2¹⁰ = 21160793 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21161857) 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 39 ways as a sum of consecutive naturals, for example, 68778 + ... + 69084.

Almost surely, 2^21161817 is an apocalyptic number.

21161817 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

It is an amenable number.

21161817 is a deficient number, since it is larger than the sum of its proper divisors (12826599).

21161817 is a wasteful number, since it uses less digits than its factorization.

21161817 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 379 (or 370 counting only the distinct ones).

The product of its digits is 672, while the sum is 27.

The square root of 21161817 is about 4600.1974957604. The cubic root of 21161817 is about 276.5992414846.

Adding to 21161817 its reverse (71816112), we get a palindrome (92977929).

The spelling of 21161817 in words is "twenty-one million, one hundred sixty-one thousand, eight hundred seventeen".