21004710721 has 4 divisors (see below), whose sum is σ = 21170102272. Its totient is φ = 20839319172.

The previous prime is 21004710679. The next prime is 21004710751. The reversal of 21004710721 is 12701740012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21004710721 - 2⁷ = 21004710593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21004710751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 82695585 + ... + 82695838.

It is an arithmetic number, because the mean of its divisors is an integer number (5292525568).

Almost surely, 2^21004710721 is an apocalyptic number.

It is an amenable number.

21004710721 is a deficient number, since it is larger than the sum of its proper divisors (165391551).

21004710721 is a wasteful number, since it uses less digits than its factorization.

21004710721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 165391550.

The product of its (nonzero) digits is 784, while the sum is 25.

The spelling of 21004710721 in words is "twenty-one billion, four million, seven hundred ten thousand, seven hundred twenty-one".