19990597921 has 8 divisors (see below), whose sum is σ = 22849026624. Its totient is φ = 17132826480.

The previous prime is 19990597903. The next prime is 19990597943. The reversal of 19990597921 is 12979509991.

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

It is not a de Polignac number, because 19990597921 - 2⁷ = 19990597793 is a prime.

It is a super-3 number, since 3×19990597921³ (a number of 32 digits) contains 333 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 19990597921.

It is not an unprimeable number, because it can be changed into a prime (19990597021) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 97315 + ... + 222376.

It is an arithmetic number, because the mean of its divisors is an integer number (2856128328).

Almost surely, 2^19990597921 is an apocalyptic number.

It is an amenable number.

19990597921 is a deficient number, since it is larger than the sum of its proper divisors (2858428703).

19990597921 is an equidigital number, since it uses as much as digits as its factorization.

19990597921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 328631.

The product of its (nonzero) digits is 4133430, while the sum is 61.

The spelling of 19990597921 in words is "nineteen billion, nine hundred ninety million, five hundred ninety-seven thousand, nine hundred twenty-one".