21544061521 has 16 divisors (see below), whose sum is σ = 23108256000. Its totient is φ = 20033120448.

The previous prime is 21544061509. The next prime is 21544061593. The reversal of 21544061521 is 12516044512.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21544061521 - 2²¹ = 21541964369 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21544061321) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1035580 + ... + 1056178.

It is an arithmetic number, because the mean of its divisors is an integer number (1444266000).

Almost surely, 2^21544061521 is an apocalyptic number.

It is an amenable number.

21544061521 is a deficient number, since it is larger than the sum of its proper divisors (1564194479).

21544061521 is a wasteful number, since it uses less digits than its factorization.

21544061521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21888.

The product of its (nonzero) digits is 9600, while the sum is 31.

The spelling of 21544061521 in words is "twenty-one billion, five hundred forty-four million, sixty-one thousand, five hundred twenty-one".