2021781 has 8 divisors (see below), whose sum is σ = 2714400. Its totient is φ = 1338512.

The previous prime is 2021779. The next prime is 2021783. The reversal of 2021781 is 1871202.

It is an interprime number because it is at equal distance from previous prime (2021779) and next prime (2021783).

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 2021781 - 2¹ = 2021779 is a prime.

It is a super-2 number, since 2×2021781² = 8175196823922, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2021783) 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, 1815 + ... + 2708.

It is an arithmetic number, because the mean of its divisors is an integer number (339300).

2^2021781 is an apocalyptic number.

It is an amenable number.

2021781 is a deficient number, since it is larger than the sum of its proper divisors (692619).

2021781 is a wasteful number, since it uses less digits than its factorization.

2021781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4675.

The product of its (nonzero) digits is 224, while the sum is 21.

The square root of 2021781 is about 1421.8934559242. The cubic root of 2021781 is about 126.4478269646.

Adding to 2021781 its reverse (1871202), we get a palindrome (3892983).

The spelling of 2021781 in words is "two million, twenty-one thousand, seven hundred eighty-one".