1961210721 has 4 divisors (see below), whose sum is σ = 2614947632. Its totient is φ = 1307473812.

The previous prime is 1961210717. The next prime is 1961210747. The reversal of 1961210721 is 1270121691.

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, and also an emirpimes, since its reverse is a distinct semiprime: 1270121691 = 3 ⋅423373897.

It is not a de Polignac number, because 1961210721 - 2² = 1961210717 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1961210701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 326868451 + ... + 326868456.

It is an arithmetic number, because the mean of its divisors is an integer number (653736908).

Almost surely, 2^1961210721 is an apocalyptic number.

It is an amenable number.

1961210721 is a deficient number, since it is larger than the sum of its proper divisors (653736911).

1961210721 is an equidigital number, since it uses as much as digits as its factorization.

1961210721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 653736910.

The product of its (nonzero) digits is 1512, while the sum is 30.

The square root of 1961210721 is about 44285.5588312940. The cubic root of 1961210721 is about 1251.7225789005.

The spelling of 1961210721 in words is "one billion, nine hundred sixty-one million, two hundred ten thousand, seven hundred twenty-one".