1921286721 has 8 divisors (see below), whose sum is σ = 2644351744. Its totient is φ = 1239539760.

The previous prime is 1921286713. The next prime is 1921286791. The reversal of 1921286721 is 1276821291.

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

It is not a de Polignac number, because 1921286721 - 2³ = 1921286713 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1921286721.

It is not an unprimeable number, because it can be changed into a prime (1921286701) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 10329406 + ... + 10329591.

It is an arithmetic number, because the mean of its divisors is an integer number (330543968).

Almost surely, 2^1921286721 is an apocalyptic number.

It is an amenable number.

1921286721 is a deficient number, since it is larger than the sum of its proper divisors (723065023).

1921286721 is a wasteful number, since it uses less digits than its factorization.

1921286721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20659031.

The product of its digits is 24192, while the sum is 39.

The square root of 1921286721 is about 43832.4847687192. The cubic root of 1921286721 is about 1243.1705890835.

The spelling of 1921286721 in words is "one billion, nine hundred twenty-one million, two hundred eighty-six thousand, seven hundred twenty-one".