21912519328561 has 3 divisors (see below), whose sum is σ = 21912524009643. Its totient is φ = 21912514647480.

The previous prime is 21912519328501. The next prime is 21912519328597. The reversal of 21912519328561 is 16582391521912.

The square root of 21912519328561 is 4681081.

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., 7081085982961 + 14831433345600 = 2661031^2 + 3851160^2 .

It is not a de Polignac number, because 21912519328561 - 2¹⁷ = 21912519197489 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21912519328501) 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, 2340541 + ... + 7021621.

It is an arithmetic number, because the mean of its divisors is an integer number (7304174669881).

Almost surely, 2^{21912519328561} is an apocalyptic number.

21912519328561 is the 4681081-st square number.

21912519328561 is the 2340541-st centered octagonal number.

It is an amenable number.

21912519328561 is a deficient number, since it is larger than the sum of its proper divisors (4681082).

21912519328561 is an frugal number, since it uses more digits than its factorization.

21912519328561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9362162 (or 4681081 counting only the distinct ones).

The product of its digits is 2332800, while the sum is 55.

The spelling of 21912519328561 in words is "twenty-one trillion, nine hundred twelve billion, five hundred nineteen million, three hundred twenty-eight thousand, five hundred sixty-one".