21207638 has 8 divisors (see below), whose sum is σ = 31838832. Its totient is φ = 10594696.

The previous prime is 21207631. The next prime is 21207649. The reversal of 21207638 is 83670212.

It is a happy number.

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

It is a self number, because there is not a number n which added to its sum of digits gives 21207638.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21207631) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1145 + ... + 6612.

It is an arithmetic number, because the mean of its divisors is an integer number (3979854).

Almost surely, 2^21207638 is an apocalyptic number.

21207638 is a deficient number, since it is larger than the sum of its proper divisors (10631194).

21207638 is a wasteful number, since it uses less digits than its factorization.

21207638 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9126.

The product of its (nonzero) digits is 4032, while the sum is 29.

The square root of 21207638 is about 4605.1751323918. The cubic root of 21207638 is about 276.7987347080.

The spelling of 21207638 in words is "twenty-one million, two hundred seven thousand, six hundred thirty-eight".