20378817821515 has 4 divisors (see below), whose sum is σ = 24454581385824. Its totient is φ = 16303054257208.

The previous prime is 20378817821503. The next prime is 20378817821533. The reversal of 20378817821515 is 51512871887302.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 20378817821515 - 2⁹ = 20378817821003 is a prime.

It is a Smith number, since the sum of its digits (58) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 20378817821515.

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, 2037881782147 + ... + 2037881782156.

It is an arithmetic number, because the mean of its divisors is an integer number (6113645346456).

Almost surely, 2^{20378817821515} is an apocalyptic number.

20378817821515 is a deficient number, since it is larger than the sum of its proper divisors (4075763564309).

20378817821515 is an equidigital number, since it uses as much as digits as its factorization.

20378817821515 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4075763564308.

The product of its (nonzero) digits is 7526400, while the sum is 58.

The spelling of 20378817821515 in words is "twenty trillion, three hundred seventy-eight billion, eight hundred seventeen million, eight hundred twenty-one thousand, five hundred fifteen".