21007905 has 8 divisors (see below), whose sum is σ = 33612672. Its totient is φ = 11204208.

The previous prime is 21007891. The next prime is 21007913. The reversal of 21007905 is 50970012.

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

It is not a de Polignac number, because 21007905 - 2⁵ = 21007873 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 700249 + ... + 700278.

It is an arithmetic number, because the mean of its divisors is an integer number (4201584).

Almost surely, 2^21007905 is an apocalyptic number.

It is an amenable number.

21007905 is a deficient number, since it is larger than the sum of its proper divisors (12604767).

21007905 is a wasteful number, since it uses less digits than its factorization.

21007905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1400535.

The product of its (nonzero) digits is 630, while the sum is 24.

The square root of 21007905 is about 4583.4381200143. The cubic root of 21007905 is about 275.9270312248.

Adding to 21007905 its reverse (50970012), we get a palindrome (71977917).

It can be divided in two parts, 21007 and 905, that added together give a palindrome (21912).

The spelling of 21007905 in words is "twenty-one million, seven thousand, nine hundred five".