21393551775 has 24 divisors (see below), whose sum is σ = 36908530560. Its totient is φ = 10913811040.

The previous prime is 21393551761. The next prime is 21393551779. The reversal of 21393551775 is 57715539312.

It is not a de Polignac number, because 21393551775 - 2¹⁴ = 21393535391 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21393551779) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 6199305 + ... + 6202754.

It is an arithmetic number, because the mean of its divisors is an integer number (1537855440).

Almost surely, 2^21393551775 is an apocalyptic number.

21393551775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21393551775 is a deficient number, since it is larger than the sum of its proper divisors (15514978785).

21393551775 is a wasteful number, since it uses less digits than its factorization.

21393551775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12402095 (or 12402090 counting only the distinct ones).

The product of its digits is 992250, while the sum is 48.

The spelling of 21393551775 in words is "twenty-one billion, three hundred ninety-three million, five hundred fifty-one thousand, seven hundred seventy-five".