21788661 has 8 divisors (see below), whose sum is σ = 29182720. Its totient is φ = 14460192.

The previous prime is 21788653. The next prime is 21788677. The reversal of 21788661 is 16688712.

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

It is not a de Polignac number, because 21788661 - 2³ = 21788653 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21788681) 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, 15616 + ... + 16953.

It is an arithmetic number, because the mean of its divisors is an integer number (3647840).

Almost surely, 2^21788661 is an apocalyptic number.

It is an amenable number.

21788661 is a deficient number, since it is larger than the sum of its proper divisors (7394059).

21788661 is a wasteful number, since it uses less digits than its factorization.

21788661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32795.

The product of its digits is 32256, while the sum is 39.

The square root of 21788661 is about 4667.8325805453. The cubic root of 21788661 is about 279.3038018549.

The spelling of 21788661 in words is "twenty-one million, seven hundred eighty-eight thousand, six hundred sixty-one".