2100781 has 2 divisors, whose sum is σ = 2100782. Its totient is φ = 2100780.

The previous prime is 2100743. The next prime is 2100793. The reversal of 2100781 is 1870012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1798281 + 302500 = 1341^2 + 550^2 .

It is a cyclic number.

It is not a de Polignac number, because 2100781 - 2⁹ = 2100269 is a prime.

It is a super-2 number, since 2×2100781² = 8826561619922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2100181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1050390 + 1050391.

It is an arithmetic number, because the mean of its divisors is an integer number (1050391).

2^2100781 is an apocalyptic number.

It is an amenable number.

2100781 is a deficient number, since it is larger than the sum of its proper divisors (1).

2100781 is an equidigital number, since it uses as much as digits as its factorization.

2100781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 112, while the sum is 19.

The square root of 2100781 is about 1449.4071201702. The cubic root of 2100781 is about 128.0737896475.

Adding to 2100781 its reverse (1870012), we get a palindrome (3970793).

The spelling of 2100781 in words is "two million, one hundred thousand, seven hundred eighty-one".