18019820021 has 24 divisors (see below), whose sum is σ = 22357028376. Its totient is φ = 14430796800.

The previous prime is 18019820017. The next prime is 18019820023. The reversal of 18019820021 is 12002891081.

It can be written as a sum of positive squares in 4 ways, for example, as 3820476100 + 14199343921 = 61810^2 + 119161^2 .

It is not a de Polignac number, because 18019820021 - 2² = 18019820017 is a prime.

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 18019820021.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18019820023) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 35171 + ... + 193071.

It is an arithmetic number, because the mean of its divisors is an integer number (931542849).

Almost surely, 2^18019820021 is an apocalyptic number.

It is an amenable number.

18019820021 is a deficient number, since it is larger than the sum of its proper divisors (4337208355).

18019820021 is a wasteful number, since it uses less digits than its factorization.

18019820021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 158069 (or 158062 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 32.

The spelling of 18019820021 in words is "eighteen billion, nineteen million, eight hundred twenty thousand, twenty-one".