18991377451 has 4 divisors (see below), whose sum is σ = 19005953872. Its totient is φ = 18976801032.

The previous prime is 18991377437. The next prime is 18991377473. The reversal of 18991377451 is 15477319981.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 18991377451 - 2⁷ = 18991377323 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 18991377392 and 18991377401.

It is not an unprimeable number, because it can be changed into a prime (18991375451) 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, 7286256 + ... + 7288861.

It is an arithmetic number, because the mean of its divisors is an integer number (4751488468).

Almost surely, 2^18991377451 is an apocalyptic number.

18991377451 is a deficient number, since it is larger than the sum of its proper divisors (14576421).

18991377451 is a wasteful number, since it uses less digits than its factorization.

18991377451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 14576420.

The product of its digits is 1905120, while the sum is 55.

The spelling of 18991377451 in words is "eighteen billion, nine hundred ninety-one million, three hundred seventy-seven thousand, four hundred fifty-one".