21521906017 has 8 divisors (see below), whose sum is σ = 22065057000. Its totient is φ = 20979623040.

The previous prime is 21521906009. The next prime is 21521906033. The reversal of 21521906017 is 71060912512.

It can be written as a sum of positive squares in 4 ways, for example, as 2512114641 + 19009791376 = 50121^2 + 137876^2 .

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 21521906017 - 2³ = 21521906009 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21521906617) 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, 166642 + ... + 266107.

It is an arithmetic number, because the mean of its divisors is an integer number (2758132125).

Almost surely, 2^21521906017 is an apocalyptic number.

It is an amenable number.

21521906017 is a deficient number, since it is larger than the sum of its proper divisors (543150983).

21521906017 is a wasteful number, since it uses less digits than its factorization.

21521906017 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 434003.

The product of its (nonzero) digits is 7560, while the sum is 34.

The spelling of 21521906017 in words is "twenty-one billion, five hundred twenty-one million, nine hundred six thousand, seventeen".