919819821 has 4 divisors (see below), whose sum is σ = 1226426432. Its totient is φ = 613213212.

The previous prime is 919819787. The next prime is 919819847. The reversal of 919819821 is 128918919.

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: 128918919 = 3 ⋅42972973.

It is not a de Polignac number, because 919819821 - 2⁶ = 919819757 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 (919819421) 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, 153303301 + ... + 153303306.

It is an arithmetic number, because the mean of its divisors is an integer number (306606608).

Almost surely, 2^919819821 is an apocalyptic number.

It is an amenable number.

919819821 is a deficient number, since it is larger than the sum of its proper divisors (306606611).

919819821 is a wasteful number, since it uses less digits than its factorization.

919819821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 306606610.

The product of its digits is 93312, while the sum is 48.

The square root of 919819821 is about 30328.5314679099. The cubic root of 919819821 is about 972.5253292901.

The spelling of 919819821 in words is "nine hundred nineteen million, eight hundred nineteen thousand, eight hundred twenty-one".