21407668 has 18 divisors (see below), whose sum is σ = 37871106. Its totient is φ = 10588464.

The previous prime is 21407663. The next prime is 21407669. The reversal of 21407668 is 86670412.

It can be written as a sum of positive squares in only one way, i.e., 15147664 + 6260004 = 3892^2 + 2502^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21407663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 77146 + ... + 77422.

Almost surely, 2^21407668 is an apocalyptic number.

It is an amenable number.

21407668 is a deficient number, since it is larger than the sum of its proper divisors (16463438).

21407668 is a wasteful number, since it uses less digits than its factorization.

21407668 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 559 (or 418 counting only the distinct ones).

The product of its (nonzero) digits is 16128, while the sum is 34.

The square root of 21407668 is about 4626.8421196319. The cubic root of 21407668 is about 277.6662661858. Note that the first 3 decimals are identical.

The spelling of 21407668 in words is "twenty-one million, four hundred seven thousand, six hundred sixty-eight".