21221689 has 8 divisors (see below), whose sum is σ = 22609440. Its totient is φ = 19861056.

The previous prime is 21221671. The next prime is 21221693. The reversal of 21221689 is 98612212.

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

It is a cyclic number.

It is not a de Polignac number, because 21221689 - 2⁵ = 21221657 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21221689.

It is not an unprimeable number, because it can be changed into a prime (21222689) 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, 5152 + ... + 8305.

It is an arithmetic number, because the mean of its divisors is an integer number (2826180).

Almost surely, 2^21221689 is an apocalyptic number.

It is an amenable number.

21221689 is a deficient number, since it is larger than the sum of its proper divisors (1387751).

21221689 is a wasteful number, since it uses less digits than its factorization.

21221689 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 13559.

The product of its digits is 3456, while the sum is 31.

The square root of 21221689 is about 4606.7004460894. The cubic root of 21221689 is about 276.8598516885.

The spelling of 21221689 in words is "twenty-one million, two hundred twenty-one thousand, six hundred eighty-nine".