21438668 has 24 divisors (see below), whose sum is σ = 39379200. Its totient is φ = 10193040.

The previous prime is 21438647. The next prime is 21438673. The reversal of 21438668 is 86683412.

It is a happy number.

It is a super-2 number, since 2×21438668² = 919232971228448, which contains 22 as substring.

It is a Smith number, since the sum of its digits (38) coincides with the sum of the digits of its prime factors.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 17723 + ... + 18893.

It is an arithmetic number, because the mean of its divisors is an integer number (1640800).

Almost surely, 2^21438668 is an apocalyptic number.

It is an amenable number.

21438668 is a deficient number, since it is larger than the sum of its proper divisors (17940532).

21438668 is a wasteful number, since it uses less digits than its factorization.

21438668 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1397 (or 1395 counting only the distinct ones).

The product of its digits is 55296, while the sum is 38.

The square root of 21438668 is about 4630.1909247892. The cubic root of 21438668 is about 277.8002291305.

The spelling of 21438668 in words is "twenty-one million, four hundred thirty-eight thousand, six hundred sixty-eight".