21218783755 has 16 divisors (see below), whose sum is σ = 27830474784. Its totient is φ = 15435383040.

The previous prime is 21218783749. The next prime is 21218783779. The reversal of 21218783755 is 55738781212.

It is not a de Polignac number, because 21218783755 - 2¹¹ = 21218781707 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21218783699 and 21218783708.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2431786 + ... + 2440495.

It is an arithmetic number, because the mean of its divisors is an integer number (1739404674).

Almost surely, 2^21218783755 is an apocalyptic number.

21218783755 is a deficient number, since it is larger than the sum of its proper divisors (6611691029).

21218783755 is a wasteful number, since it uses less digits than its factorization.

21218783755 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4872366.

The product of its digits is 940800, while the sum is 49.

The spelling of 21218783755 in words is "twenty-one billion, two hundred eighteen million, seven hundred eighty-three thousand, seven hundred fifty-five".