21393906 has 16 divisors (see below), whose sum is σ = 44168448. Its totient is φ = 6901200.

The previous prime is 21393899. The next prime is 21393917. The reversal of 21393906 is 60939312.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 57325 + ... + 57696.

It is an arithmetic number, because the mean of its divisors is an integer number (2760528).

Almost surely, 2^21393906 is an apocalyptic number.

21393906 is an abundant number, since it is smaller than the sum of its proper divisors (22774542).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21393906 is a wasteful number, since it uses less digits than its factorization.

21393906 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115057.

The product of its (nonzero) digits is 8748, while the sum is 33.

The square root of 21393906 is about 4625.3546891022. The cubic root of 21393906 is about 277.6067538297.

The spelling of 21393906 in words is "twenty-one million, three hundred ninety-three thousand, nine hundred six".