21683668 has 6 divisors (see below), whose sum is σ = 37946426. Its totient is φ = 10841832.

The previous prime is 21683659. The next prime is 21683699. The reversal of 21683668 is 86638612.

It can be written as a sum of positive squares in only one way, i.e., 19909444 + 1774224 = 4462^2 + 1332^2 .

It is a self number, because there is not a number n which added to its sum of digits gives 21683668.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2710455 + ... + 2710462.

Almost surely, 2^21683668 is an apocalyptic number.

It is an amenable number.

21683668 is a deficient number, since it is larger than the sum of its proper divisors (16262758).

21683668 is a wasteful number, since it uses less digits than its factorization.

21683668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5420921 (or 5420919 counting only the distinct ones).

The product of its digits is 82944, while the sum is 40.

The square root of 21683668 is about 4656.5725592972. The cubic root of 21683668 is about 278.8544523322.

The spelling of 21683668 in words is "twenty-one million, six hundred eighty-three thousand, six hundred sixty-eight".