2101781 has 4 divisors (see below), whose sum is σ = 2292864. Its totient is φ = 1910700.

The previous prime is 2101751. The next prime is 2101789. The reversal of 2101781 is 1871012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a de Polignac number, because none of the positive numbers 2^k-2101781 is a prime.

It is a super-2 number, since 2×2101781² = 8834966743922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2101789) 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, 95525 + ... + 95546.

It is an arithmetic number, because the mean of its divisors is an integer number (573216).

2^2101781 is an apocalyptic number.

It is an amenable number.

2101781 is a deficient number, since it is larger than the sum of its proper divisors (191083).

2101781 is a wasteful number, since it uses less digits than its factorization.

2101781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191082.

The product of its (nonzero) digits is 112, while the sum is 20.

The square root of 2101781 is about 1449.7520477654. The cubic root of 2101781 is about 128.0941080391.

Adding to 2101781 its reverse (1871012), we get a palindrome (3972793).

It can be divided in two parts, 2101 and 781, that added together give a palindrome (2882).

The spelling of 2101781 in words is "two million, one hundred one thousand, seven hundred eighty-one".