21397438 has 8 divisors (see below), whose sum is σ = 32115888. Its totient is φ = 10692144.

The previous prime is 21397427. The next prime is 21397451. The reversal of 21397438 is 83479312.

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

It is a junction number, because it is equal to n+sod(n) for n = 21397397 and 21397406.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4095 + ... + 7717.

It is an arithmetic number, because the mean of its divisors is an integer number (4014486).

Almost surely, 2^21397438 is an apocalyptic number.

21397438 is a deficient number, since it is larger than the sum of its proper divisors (10718450).

21397438 is a wasteful number, since it uses less digits than its factorization.

21397438 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6578.

The product of its digits is 36288, while the sum is 37.

The square root of 21397438 is about 4625.7364819021. The cubic root of 21397438 is about 277.6220300350.

The spelling of 21397438 in words is "twenty-one million, three hundred ninety-seven thousand, four hundred thirty-eight".