18121780 has 12 divisors (see below), whose sum is σ = 38055780. Its totient is φ = 7248704.

The previous prime is 18121777. The next prime is 18121783. The reversal of 18121780 is 8712181.

It is an interprime number because it is at equal distance from previous prime (18121777) and next prime (18121783).

It can be written as a sum of positive squares in 2 ways, for example, as 4857616 + 13264164 = 2204^2 + 3642^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18121783) 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, 453025 + ... + 453064.

It is an arithmetic number, because the mean of its divisors is an integer number (3171315).

Almost surely, 2^18121780 is an apocalyptic number.

18121780 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

18121780 is an abundant number, since it is smaller than the sum of its proper divisors (19934000).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

18121780 is a wasteful number, since it uses less digits than its factorization.

18121780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 906098 (or 906096 counting only the distinct ones).

The product of its (nonzero) digits is 896, while the sum is 28.

The square root of 18121780 is about 4256.9684048628. The cubic root of 18121780 is about 262.6638372524.

The spelling of 18121780 in words is "eighteen million, one hundred twenty-one thousand, seven hundred eighty".