1921550399 has 4 divisors (see below), whose sum is σ = 1921657320. Its totient is φ = 1921443480.

The previous prime is 1921550369. The next prime is 1921550437. The reversal of 1921550399 is 9930551291.

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 is a cyclic number.

It is not a de Polignac number, because 1921550399 - 2²⁰ = 1920501823 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1921550369) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19172 + ... + 64889.

It is an arithmetic number, because the mean of its divisors is an integer number (480414330).

Almost surely, 2^1921550399 is an apocalyptic number.

1921550399 is a deficient number, since it is larger than the sum of its proper divisors (106921).

1921550399 is an equidigital number, since it uses as much as digits as its factorization.

1921550399 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 106920.

The product of its (nonzero) digits is 109350, while the sum is 44.

The square root of 1921550399 is about 43835.4924575965. The cubic root of 1921550399 is about 1243.2274575243.

The spelling of 1921550399 in words is "one billion, nine hundred twenty-one million, five hundred fifty thousand, three hundred ninety-nine".