1921520721 has 8 divisors (see below), whose sum is σ = 2563362144. Its totient is φ = 1280346560.

The previous prime is 1921520701. The next prime is 1921520737. The reversal of 1921520721 is 1270251291.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1921520721 - 2¹¹ = 1921518673 is a prime.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (1921520701) 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 7 ways as a sum of consecutive naturals, for example, 160056 + ... + 171641.

It is an arithmetic number, because the mean of its divisors is an integer number (320420268).

Almost surely, 2^1921520721 is an apocalyptic number.

It is an amenable number.

1921520721 is a deficient number, since it is larger than the sum of its proper divisors (641841423).

1921520721 is a wasteful number, since it uses less digits than its factorization.

1921520721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 333631.

The product of its (nonzero) digits is 2520, while the sum is 30.

The square root of 1921520721 is about 43835.1539406445. The cubic root of 1921520721 is about 1243.2210570166.

The spelling of 1921520721 in words is "one billion, nine hundred twenty-one million, five hundred twenty thousand, seven hundred twenty-one".