21393907 has 4 divisors (see below), whose sum is σ = 21547960. Its totient is φ = 21239856.

The previous prime is 21393899. The next prime is 21393917. The reversal of 21393907 is 70939312.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21393907 - 2³ = 21393899 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21393917) 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, 76818 + ... + 77095.

It is an arithmetic number, because the mean of its divisors is an integer number (5386990).

Almost surely, 2^21393907 is an apocalyptic number.

21393907 is a deficient number, since it is larger than the sum of its proper divisors (154053).

21393907 is a wasteful number, since it uses less digits than its factorization.

21393907 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 154052.

The product of its (nonzero) digits is 10206, while the sum is 34.

The square root of 21393907 is about 4625.3547972020. The cubic root of 21393907 is about 277.6067581550.

The spelling of 21393907 in words is "twenty-one million, three hundred ninety-three thousand, nine hundred seven".