21019980 has 48 divisors (see below), whose sum is σ = 59157504. Its totient is φ = 5576640.

The previous prime is 21019979. The next prime is 21019981. The reversal of 21019980 is 8991012.

It is an interprime number because it is at equal distance from previous prime (21019979) and next prime (21019981).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is not an unprimeable number, because it can be changed into a prime (21019981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 12595 + ... + 14165.

It is an arithmetic number, because the mean of its divisors is an integer number (1232448).

Almost surely, 2^21019980 is an apocalyptic number.

21019980 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21019980 is an abundant number, since it is smaller than the sum of its proper divisors (38137524).

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

21019980 is a wasteful number, since it uses less digits than its factorization.

21019980 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1806 (or 1804 counting only the distinct ones).

The product of its (nonzero) digits is 1296, while the sum is 30.

The square root of 21019980 is about 4584.7551733980. The cubic root of 21019980 is about 275.9798872132.

The spelling of 21019980 in words is "twenty-one million, nineteen thousand, nine hundred eighty".