21687512755 has 4 divisors (see below), whose sum is σ = 26025015312. Its totient is φ = 17350010200.

The previous prime is 21687512711. The next prime is 21687512767. The reversal of 21687512755 is 55721578612.

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

It is not a de Polignac number, because 21687512755 - 2¹¹ = 21687510707 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21687512699 and 21687512708.

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, 2168751271 + ... + 2168751280.

It is an arithmetic number, because the mean of its divisors is an integer number (6506253828).

Almost surely, 2^21687512755 is an apocalyptic number.

21687512755 is a deficient number, since it is larger than the sum of its proper divisors (4337502557).

21687512755 is an equidigital number, since it uses as much as digits as its factorization.

21687512755 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4337502556.

The product of its digits is 1176000, while the sum is 49.

The spelling of 21687512755 in words is "twenty-one billion, six hundred eighty-seven million, five hundred twelve thousand, seven hundred fifty-five".