21815748417953 has 4 divisors (see below), whose sum is σ = 24932283906240. Its totient is φ = 18699212929668.

The previous prime is 21815748417943. The next prime is 21815748417973. The reversal of 21815748417953 is 35971484751812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21815748417953 - 2³⁴ = 21798568548769 is a prime.

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 21815748417953.

It is not an unprimeable number, because it can be changed into a prime (21815748417943) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (29) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1558267744133 + ... + 1558267744146.

It is an arithmetic number, because the mean of its divisors is an integer number (6233070976560).

Almost surely, 2^{21815748417953} is an apocalyptic number.

It is an amenable number.

21815748417953 is a deficient number, since it is larger than the sum of its proper divisors (3116535488287).

21815748417953 is an equidigital number, since it uses as much as digits as its factorization.

21815748417953 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3116535488286.

The product of its digits is 67737600, while the sum is 65.

The spelling of 21815748417953 in words is "twenty-one trillion, eight hundred fifteen billion, seven hundred forty-eight million, four hundred seventeen thousand, nine hundred fifty-three".