16393397621 has 4 divisors (see below), whose sum is σ = 16434691212. Its totient is φ = 16352104032.

The previous prime is 16393397609. The next prime is 16393397681. The reversal of 16393397621 is 12679339361.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 12679339361 = 13 ⋅975333797.

It can be written as a sum of positive squares in 2 ways, for example, as 12385241521 + 4008156100 = 111289^2 + 63310^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-16393397621 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 16393397621.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (16393397681) 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, 20646200 + ... + 20646993.

It is an arithmetic number, because the mean of its divisors is an integer number (4108672803).

Almost surely, 2^16393397621 is an apocalyptic number.

It is an amenable number.

16393397621 is a deficient number, since it is larger than the sum of its proper divisors (41293591).

16393397621 is an equidigital number, since it uses as much as digits as its factorization.

16393397621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41293590.

The product of its digits is 1102248, while the sum is 50.

The spelling of 16393397621 in words is "sixteen billion, three hundred ninety-three million, three hundred ninety-seven thousand, six hundred twenty-one".