2145121681 has 16 divisors (see below), whose sum is σ = 2238163200. Its totient is φ = 2054332800.

The previous prime is 2145121673. The next prime is 2145121691. The reversal of 2145121681 is 1861215412.

It is a cyclic number.

It is not a de Polignac number, because 2145121681 - 2³ = 2145121673 is a prime.

It is a super-2 number, since 2×2145121681² = 9203094052592531522, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2145121661) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 584430 + ... + 588088.

It is an arithmetic number, because the mean of its divisors is an integer number (139885200).

Almost surely, 2^2145121681 is an apocalyptic number.

It is an amenable number.

2145121681 is a deficient number, since it is larger than the sum of its proper divisors (93041519).

2145121681 is a wasteful number, since it uses less digits than its factorization.

2145121681 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3960.

The product of its digits is 3840, while the sum is 31.

The square root of 2145121681 is about 46315.4583373629. The cubic root of 2145121681 is about 1289.6859762848.

The spelling of 2145121681 in words is "two billion, one hundred forty-five million, one hundred twenty-one thousand, six hundred eighty-one".