21388247597 has 4 divisors (see below), whose sum is σ = 21511879260. Its totient is φ = 21264615936.

The previous prime is 21388247581. The next prime is 21388247599. The reversal of 21388247597 is 79574288312.

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 19787767561 + 1600480036 = 140669^2 + 40006^2 .

It is a cyclic number.

It is not a de Polignac number, because 21388247597 - 2⁴ = 21388247581 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21388247599) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 61815572 + ... + 61815917.

It is an arithmetic number, because the mean of its divisors is an integer number (5377969815).

Almost surely, 2^21388247597 is an apocalyptic number.

It is an amenable number.

21388247597 is a deficient number, since it is larger than the sum of its proper divisors (123631663).

21388247597 is a wasteful number, since it uses less digits than its factorization.

21388247597 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123631662.

The product of its digits is 6773760, while the sum is 56.

The spelling of 21388247597 in words is "twenty-one billion, three hundred eighty-eight million, two hundred forty-seven thousand, five hundred ninety-seven".