18821772 has 18 divisors (see below), whose sum is σ = 47577348. Its totient is φ = 6273912.

The previous prime is 18821753. The next prime is 18821779. The reversal of 18821772 is 27712881.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (18).

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36), and also a Moran number because the ratio is a prime number: 522827 = 18821772 / (1 + 8 + 8 + 2 + 1 + 7 + 7 + 2).

It is not an unprimeable number, because it can be changed into a prime (18821779) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 261378 + ... + 261449.

It is an arithmetic number, because the mean of its divisors is an integer number (2643186).

Almost surely, 2^18821772 is an apocalyptic number.

18821772 is a gapful number since it is divisible by the number (12) formed by its first and last digit.

It is an amenable number.

18821772 is an abundant number, since it is smaller than the sum of its proper divisors (28755576).

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

18821772 is a wasteful number, since it uses less digits than its factorization.

18821772 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 522837 (or 522832 counting only the distinct ones).

The product of its digits is 12544, while the sum is 36.

The square root of 18821772 is about 4338.4066199470. The cubic root of 18821772 is about 266.0031846152.

The spelling of 18821772 in words is "eighteen million, eight hundred twenty-one thousand, seven hundred seventy-two".