21364720437617 has 4 divisors (see below), whose sum is σ = 21364751218800. Its totient is φ = 21364689656436.

The previous prime is 21364720437601. The next prime is 21364720437631. The reversal of 21364720437617 is 71673402746312.

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 21364720437617 - 2⁴ = 21364720437601 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21364720437667) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14324867 + ... + 15745832.

It is an arithmetic number, because the mean of its divisors is an integer number (5341187804700).

Almost surely, 2^{21364720437617} is an apocalyptic number.

It is an amenable number.

21364720437617 is a deficient number, since it is larger than the sum of its proper divisors (30781183).

21364720437617 is an equidigital number, since it uses as much as digits as its factorization.

21364720437617 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30781182.

The product of its (nonzero) digits is 7112448, while the sum is 53.

The spelling of 21364720437617 in words is "twenty-one trillion, three hundred sixty-four billion, seven hundred twenty million, four hundred thirty-seven thousand, six hundred seventeen".