21201345521 has 8 divisors (see below), whose sum is σ = 21749063424. Its totient is φ = 20656112400.

The previous prime is 21201345499. The next prime is 21201345523. The reversal of 21201345521 is 12554310212.

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 21201345521 - 2¹⁸ = 21201083377 is a prime.

It is a super-2 number, since 2×21201345521² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21201345523) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 603905 + ... + 638046.

It is an arithmetic number, because the mean of its divisors is an integer number (2718632928).

Almost surely, 2^21201345521 is an apocalyptic number.

It is an amenable number.

21201345521 is a deficient number, since it is larger than the sum of its proper divisors (547717903).

21201345521 is a wasteful number, since it uses less digits than its factorization.

21201345521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1242391.

The product of its (nonzero) digits is 2400, while the sum is 26.

Adding to 21201345521 its reverse (12554310212), we get a palindrome (33755655733).

The spelling of 21201345521 in words is "twenty-one billion, two hundred one million, three hundred forty-five thousand, five hundred twenty-one".