2154193681 has 4 divisors (see below), whose sum is σ = 2154295332. Its totient is φ = 2154092032.

The previous prime is 2154193673. The next prime is 2154193729. The reversal of 2154193681 is 1863914512.

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 can be written as a sum of positive squares in 2 ways, for example, as 1504198656 + 649995025 = 38784^2 + 25495^2 .

It is a cyclic number.

It is not a de Polignac number, because 2154193681 - 2³ = 2154193673 is a prime.

It is a super-2 number, since 2×2154193681² = 9281100830520659522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2154193651) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5656 + ... + 65881.

It is an arithmetic number, because the mean of its divisors is an integer number (538573833).

Almost surely, 2^2154193681 is an apocalyptic number.

It is an amenable number.

2154193681 is a deficient number, since it is larger than the sum of its proper divisors (101651).

2154193681 is an equidigital number, since it uses as much as digits as its factorization.

2154193681 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 101650.

The product of its digits is 51840, while the sum is 40.

The square root of 2154193681 is about 46413.2920724225. The cubic root of 2154193681 is about 1291.5015028460.

The spelling of 2154193681 in words is "two billion, one hundred fifty-four million, one hundred ninety-three thousand, six hundred eighty-one".