2135781 has 8 divisors (see below), whose sum is σ = 3164160. Its totient is φ = 1423836.

The previous prime is 2135779. The next prime is 2135797. The reversal of 2135781 is 1875312.

It is not a de Polignac number, because 2135781 - 2¹ = 2135779 is a prime.

It is a super-2 number, since 2×2135781² = 9123120959922, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 79103 = 2135781 / (2 + 1 + 3 + 5 + 7 + 8 + 1).

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2135701) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39525 + ... + 39578.

It is an arithmetic number, because the mean of its divisors is an integer number (395520).

2^2135781 is an apocalyptic number.

It is an amenable number.

2135781 is a deficient number, since it is larger than the sum of its proper divisors (1028379).

2135781 is an equidigital number, since it uses as much as digits as its factorization.

2135781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 79112 (or 79106 counting only the distinct ones).

The product of its digits is 1680, while the sum is 27.

The square root of 2135781 is about 1461.4311478821. The cubic root of 2135781 is about 128.7811323841.

It can be divided in two parts, 2135 and 781, that added together give a square (2916 = 54²).

The spelling of 2135781 in words is "two million, one hundred thirty-five thousand, seven hundred eighty-one".