21585780241 has 3 divisors (see below), whose sum is σ = 21585927163. Its totient is φ = 21585633320.

The previous prime is 21585780211. The next prime is 21585780247. The reversal of 21585780241 is 14208758512.

The square root of 21585780241 is 146921.

It is a perfect power (a square), and thus also a powerful number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 3349978641 + 18235801600 = 57879^2 + 135040^2 .

It is not a de Polignac number, because 21585780241 - 2⁷ = 21585780113 is a prime.

It is a super-2 number, since 2×21585780241² (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 (21585780247) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 73461 + ... + 220381.

Almost surely, 2^21585780241 is an apocalyptic number.

21585780241 is the 146921-st square number.

21585780241 is the 73461-st centered octagonal number.

It is an amenable number.

21585780241 is a deficient number, since it is larger than the sum of its proper divisors (146922).

21585780241 is an frugal number, since it uses more digits than its factorization.

21585780241 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 293842 (or 146921 counting only the distinct ones).

The product of its (nonzero) digits is 179200, while the sum is 43.

The spelling of 21585780241 in words is "twenty-one billion, five hundred eighty-five million, seven hundred eighty thousand, two hundred forty-one".