21521205329 has 4 divisors (see below), whose sum is σ = 23176682676. Its totient is φ = 19865727984.

The previous prime is 21521205253. The next prime is 21521205371. The reversal of 21521205329 is 92350212512.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 2346433600 + 19174771729 = 48440^2 + 138473^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21521205329 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21521205295 and 21521205304.

It is not an unprimeable number, because it can be changed into a prime (21521205229) 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, 827738654 + ... + 827738679.

It is an arithmetic number, because the mean of its divisors is an integer number (5794170669).

Almost surely, 2^21521205329 is an apocalyptic number.

It is an amenable number.

21521205329 is a deficient number, since it is larger than the sum of its proper divisors (1655477347).

21521205329 is a wasteful number, since it uses less digits than its factorization.

21521205329 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1655477346.

The product of its (nonzero) digits is 10800, while the sum is 32.

The spelling of 21521205329 in words is "twenty-one billion, five hundred twenty-one million, two hundred five thousand, three hundred twenty-nine".