21375061504565 has 4 divisors (see below), whose sum is σ = 25650073805484. Its totient is φ = 17100049203648.

The previous prime is 21375061504481. The next prime is 21375061504579. The reversal of 21375061504565 is 56540516057312.

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 7236325961764 + 14138735542801 = 2690042^2 + 3760151^2 .

It is a cyclic number.

It is not a de Polignac number, because 21375061504565 - 2¹⁴ = 21375061488181 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2137506150452 + ... + 2137506150461.

It is an arithmetic number, because the mean of its divisors is an integer number (6412518451371).

Almost surely, 2^{21375061504565} is an apocalyptic number.

It is an amenable number.

21375061504565 is a deficient number, since it is larger than the sum of its proper divisors (4275012300919).

21375061504565 is an equidigital number, since it uses as much as digits as its factorization.

21375061504565 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4275012300918.

The product of its (nonzero) digits is 3780000, while the sum is 50.

The spelling of 21375061504565 in words is "twenty-one trillion, three hundred seventy-five billion, sixty-one million, five hundred four thousand, five hundred sixty-five".