21004905 has 8 divisors (see below), whose sum is σ = 33607872. Its totient is φ = 11202608.

The previous prime is 21004901. The next prime is 21004909. The reversal of 21004905 is 50940012.

It is an interprime number because it is at equal distance from previous prime (21004901) and next prime (21004909).

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

It is a cyclic number.

It is not a de Polignac number, because 21004905 - 2² = 21004901 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21004901) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 700149 + ... + 700178.

It is an arithmetic number, because the mean of its divisors is an integer number (4200984).

Almost surely, 2^21004905 is an apocalyptic number.

It is an amenable number.

21004905 is a deficient number, since it is larger than the sum of its proper divisors (12602967).

21004905 is a wasteful number, since it uses less digits than its factorization.

21004905 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1400335.

The product of its (nonzero) digits is 360, while the sum is 21.

The square root of 21004905 is about 4583.1108430846. The cubic root of 21004905 is about 275.9138961613.

Adding to 21004905 its reverse (50940012), we get a palindrome (71944917).

The spelling of 21004905 in words is "twenty-one million, four thousand, nine hundred five".