18721428 has 24 divisors (see below), whose sum is σ = 47654880. Its totient is φ = 5673120.

The previous prime is 18721421. The next prime is 18721429. The reversal of 18721428 is 82412781.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (33).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (18721421) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 70783 + ... + 71046.

It is an arithmetic number, because the mean of its divisors is an integer number (1985620).

Almost surely, 2^18721428 is an apocalyptic number.

It is an amenable number.

18721428 is an abundant number, since it is smaller than the sum of its proper divisors (28933452).

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

18721428 is a wasteful number, since it uses less digits than its factorization.

18721428 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141847 (or 141845 counting only the distinct ones).

The product of its digits is 7168, while the sum is 33.

The square root of 18721428 is about 4326.8265507182. The cubic root of 18721428 is about 265.5296302240.

The spelling of 18721428 in words is "eighteen million, seven hundred twenty-one thousand, four hundred twenty-eight".