21551617 has 8 divisors (see below), whose sum is σ = 22014720. Its totient is φ = 21093600.

The previous prime is 21551591. The next prime is 21551623. The reversal of 21551617 is 71615512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21551617 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21551627) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7992 + ... + 10342.

It is an arithmetic number, because the mean of its divisors is an integer number (2751840).

Almost surely, 2^21551617 is an apocalyptic number.

It is an amenable number.

21551617 is a deficient number, since it is larger than the sum of its proper divisors (463103).

21551617 is a wasteful number, since it uses less digits than its factorization.

21551617 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2543.

The product of its digits is 2100, while the sum is 28.

The square root of 21551617 is about 4642.3719153036. The cubic root of 21551617 is about 278.2872356835.

The spelling of 21551617 in words is "twenty-one million, five hundred fifty-one thousand, six hundred seventeen".