2181749551 has 4 divisors (see below), whose sum is σ = 2181854392. Its totient is φ = 2181644712.

The previous prime is 2181749543. The next prime is 2181749561. The reversal of 2181749551 is 1559471812.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 2181749551 - 2³ = 2181749543 is a prime.

It is a super-2 number, since 2×2181749551² = 9520062206577403202, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 2181749498 and 2181749507.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2181749561) 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, 9480 + ... + 66733.

It is an arithmetic number, because the mean of its divisors is an integer number (545463598).

Almost surely, 2^2181749551 is an apocalyptic number.

2181749551 is a deficient number, since it is larger than the sum of its proper divisors (104841).

2181749551 is an equidigital number, since it uses as much as digits as its factorization.

2181749551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 104840.

The product of its digits is 100800, while the sum is 43.

The square root of 2181749551 is about 46709.2019948960. The cubic root of 2181749551 is about 1296.9850349805.

The spelling of 2181749551 in words is "two billion, one hundred eighty-one million, seven hundred forty-nine thousand, five hundred fifty-one".