21393842 has 8 divisors (see below), whose sum is σ = 32232816. Its totient is φ = 10649572.

The previous prime is 21393809. The next prime is 21393847. The reversal of 21393842 is 24839312.

It is a happy number.

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 = 21393799 and 21393808.

It is not an unprimeable number, because it can be changed into a prime (21393847) 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, 23108 + ... + 24015.

It is an arithmetic number, because the mean of its divisors is an integer number (4029102).

Almost surely, 2^21393842 is an apocalyptic number.

21393842 is a deficient number, since it is larger than the sum of its proper divisors (10838974).

21393842 is a wasteful number, since it uses less digits than its factorization.

21393842 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47352.

The product of its digits is 10368, while the sum is 32.

The square root of 21393842 is about 4625.3477707087. The cubic root of 21393842 is about 277.6064770087.

The spelling of 21393842 in words is "twenty-one million, three hundred ninety-three thousand, eight hundred forty-two".