21617849 has 4 divisors (see below), whose sum is σ = 23583120. Its totient is φ = 19652580.

The previous prime is 21617837. The next prime is 21617857. The reversal of 21617849 is 94871612.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21617849 - 2²⁰ = 20569273 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21617809) 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, 982619 + ... + 982640.

It is an arithmetic number, because the mean of its divisors is an integer number (5895780).

Almost surely, 2^21617849 is an apocalyptic number.

It is an amenable number.

21617849 is a deficient number, since it is larger than the sum of its proper divisors (1965271).

21617849 is a wasteful number, since it uses less digits than its factorization.

21617849 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1965270.

The product of its digits is 24192, while the sum is 38.

The square root of 21617849 is about 4649.4998655769. The cubic root of 21617849 is about 278.5720197477.

The spelling of 21617849 in words is "twenty-one million, six hundred seventeen thousand, eight hundred forty-nine".