21663412 has 6 divisors (see below), whose sum is σ = 37910978. Its totient is φ = 10831704.

The previous prime is 21663409. The next prime is 21663413. The reversal of 21663412 is 21436612.

It can be written as a sum of positive squares in only one way, i.e., 20466576 + 1196836 = 4524^2 + 1094^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21663413) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2707923 + ... + 2707930.

Almost surely, 2^21663412 is an apocalyptic number.

It is an amenable number.

21663412 is a deficient number, since it is larger than the sum of its proper divisors (16247566).

21663412 is a wasteful number, since it uses less digits than its factorization.

21663412 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5415857 (or 5415855 counting only the distinct ones).

The product of its digits is 1728, while the sum is 25.

The square root of 21663412 is about 4654.3970608447. The cubic root of 21663412 is about 278.7675937872.

The spelling of 21663412 in words is "twenty-one million, six hundred sixty-three thousand, four hundred twelve".