21388007 has 4 divisors (see below), whose sum is σ = 21398616. Its totient is φ = 21377400.

The previous prime is 21387973. The next prime is 21388009. The reversal of 21388007 is 70088312.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21388007 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388009) 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, 1244 + ... + 6657.

It is an arithmetic number, because the mean of its divisors is an integer number (5349654).

Almost surely, 2^21388007 is an apocalyptic number.

21388007 is a deficient number, since it is larger than the sum of its proper divisors (10609).

21388007 is an equidigital number, since it uses as much as digits as its factorization.

21388007 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10608.

The product of its (nonzero) digits is 2688, while the sum is 29.

The square root of 21388007 is about 4624.7169643125. The cubic root of 21388007 is about 277.5812363953.

The spelling of 21388007 in words is "twenty-one million, three hundred eighty-eight thousand, seven".