1921323781 has 8 divisors (see below), whose sum is σ = 2069680760. Its totient is φ = 1773047232.

The previous prime is 1921323773. The next prime is 1921323821. The reversal of 1921323781 is 1873231291.

It can be written as a sum of positive squares in 4 ways, for example, as 493239681 + 1428084100 = 22209^2 + 37790^2 .

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 1921323781 - 2³ = 1921323773 is a prime.

It is a super-2 number, since 2×1921323781² = 7382970142872271922, which contains 22 as substring.

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 1921323781.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1921323751) 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, 35155 + ... + 71263.

It is an arithmetic number, because the mean of its divisors is an integer number (258710095).

Almost surely, 2^1921323781 is an apocalyptic number.

It is an amenable number.

1921323781 is a deficient number, since it is larger than the sum of its proper divisors (148356979).

1921323781 is a wasteful number, since it uses less digits than its factorization.

1921323781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 40215.

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

The square root of 1921323781 is about 43832.9075125071. The cubic root of 1921323781 is about 1243.1785822694.

The spelling of 1921323781 in words is "one billion, nine hundred twenty-one million, three hundred twenty-three thousand, seven hundred eighty-one".