19878021 has 32 divisors (see below), whose sum is σ = 31104000. Its totient is φ = 12527424.

The previous prime is 19878011. The next prime is 19878041. The reversal of 19878021 is 12087891.

It is not a de Polignac number, because 19878021 - 2¹⁸ = 19615877 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19878011) 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 31 ways as a sum of consecutive naturals, for example, 41260 + ... + 41738.

It is an arithmetic number, because the mean of its divisors is an integer number (972000).

Almost surely, 2^19878021 is an apocalyptic number.

It is an amenable number.

19878021 is a deficient number, since it is larger than the sum of its proper divisors (11225979).

19878021 is a wasteful number, since it uses less digits than its factorization.

19878021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 570 (or 564 counting only the distinct ones).

The product of its (nonzero) digits is 8064, while the sum is 36.

The square root of 19878021 is about 4458.4774306931. The cubic root of 19878021 is about 270.8887993907. Note that the first 3 decimals are identical.

The spelling of 19878021 in words is "nineteen million, eight hundred seventy-eight thousand, twenty-one".