19979820 has 144 divisors (see below), whose sum is σ = 70394688. Its totient is φ = 4492800.

The previous prime is 19979807. The next prime is 19979891. The reversal of 19979820 is 2897991.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 127182 + ... + 127338.

It is an arithmetic number, because the mean of its divisors is an integer number (488852).

Almost surely, 2^19979820 is an apocalyptic number.

19979820 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 19979820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35197344).

19979820 is an abundant number, since it is smaller than the sum of its proper divisors (50414868).

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

19979820 is a wasteful number, since it uses less digits than its factorization.

19979820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280 (or 275 counting only the distinct ones).

The product of its (nonzero) digits is 81648, while the sum is 45.

The square root of 19979820 is about 4469.8791929984. The cubic root of 19979820 is about 271.3504360242.

The spelling of 19979820 in words is "nineteen million, nine hundred seventy-nine thousand, eight hundred twenty".