21983781 has 8 divisors (see below), whose sum is σ = 29396160. Its totient is φ = 14613632.

The previous prime is 21983747. The next prime is 21983807. The reversal of 21983781 is 18738912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21983781 - 2¹¹ = 21981733 is a prime.

It is a super-2 number, since 2×21983781² = 966573254111922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21983701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9321 + ... + 11438.

It is an arithmetic number, because the mean of its divisors is an integer number (3674520).

Almost surely, 2^21983781 is an apocalyptic number.

It is an amenable number.

21983781 is a deficient number, since it is larger than the sum of its proper divisors (7412379).

21983781 is a wasteful number, since it uses less digits than its factorization.

21983781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21115.

The product of its digits is 24192, while the sum is 39.

The square root of 21983781 is about 4688.6864898391. The cubic root of 21983781 is about 280.1350581435.

The spelling of 21983781 in words is "twenty-one million, nine hundred eighty-three thousand, seven hundred eighty-one".