1961406721 has 4 divisors (see below), whose sum is σ = 1961522244. Its totient is φ = 1961291200.

The previous prime is 1961406701. The next prime is 1961406757. The reversal of 1961406721 is 1276041691.

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 735006321 + 1226400400 = 27111^2 + 35020^2 .

It is a cyclic number.

It is not a de Polignac number, because 1961406721 - 2²⁹ = 1424535809 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1961406701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26740 + ... + 68101.

It is an arithmetic number, because the mean of its divisors is an integer number (490380561).

Almost surely, 2^1961406721 is an apocalyptic number.

It is an amenable number.

1961406721 is a deficient number, since it is larger than the sum of its proper divisors (115523).

1961406721 is an equidigital number, since it uses as much as digits as its factorization.

1961406721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 115522.

The product of its (nonzero) digits is 18144, while the sum is 37.

The square root of 1961406721 is about 44287.7716870018. The cubic root of 1961406721 is about 1251.7642758397.

The spelling of 1961406721 in words is "one billion, nine hundred sixty-one million, four hundred six thousand, seven hundred twenty-one".