21781779983 has 4 divisors (see below), whose sum is σ = 21782720448. Its totient is φ = 21780839520.

The previous prime is 21781779961. The next prime is 21781779991. The reversal of 21781779983 is 38997718712.

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 21781779983 - 2³⁴ = 4601910799 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 (21781779913) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 434591 + ... + 482112.

It is an arithmetic number, because the mean of its divisors is an integer number (5445680112).

Almost surely, 2^21781779983 is an apocalyptic number.

21781779983 is a deficient number, since it is larger than the sum of its proper divisors (940465).

21781779983 is an equidigital number, since it uses as much as digits as its factorization.

21781779983 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 940464.

The product of its digits is 10668672, while the sum is 62.

The spelling of 21781779983 in words is "twenty-one billion, seven hundred eighty-one million, seven hundred seventy-nine thousand, nine hundred eighty-three".