21124756787 has 4 divisors (see below), whose sum is σ = 21259309536. Its totient is φ = 20990204040.

The previous prime is 21124756769. The next prime is 21124756799. The reversal of 21124756787 is 78765742112.

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

It is a cyclic number.

It is not a de Polignac number, because 21124756787 - 2¹⁰ = 21124755763 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21124756987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 67276139 + ... + 67276452.

It is an arithmetic number, because the mean of its divisors is an integer number (5314827384).

Almost surely, 2^21124756787 is an apocalyptic number.

21124756787 is a deficient number, since it is larger than the sum of its proper divisors (134552749).

21124756787 is a wasteful number, since it uses less digits than its factorization.

21124756787 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 134552748.

The product of its digits is 1317120, while the sum is 50.

The spelling of 21124756787 in words is "twenty-one billion, one hundred twenty-four million, seven hundred fifty-six thousand, seven hundred eighty-seven".