19928821 has 6 divisors (see below), whose sum is σ = 21905366. Its totient is φ = 18117000.

The previous prime is 19928813. The next prime is 19928827. The reversal of 19928821 is 12882991.

It can be written as a sum of positive squares in only one way, i.e., 19847025 + 81796 = 4455^2 + 286^2 .

It is not a de Polignac number, because 19928821 - 2³ = 19928813 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19928827) 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, 82230 + ... + 82471.

Almost surely, 2^19928821 is an apocalyptic number.

19928821 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

19928821 is a deficient number, since it is larger than the sum of its proper divisors (1976545).

19928821 is a wasteful number, since it uses less digits than its factorization.

19928821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 164723 (or 164712 counting only the distinct ones).

The product of its digits is 20736, while the sum is 40.

The square root of 19928821 is about 4464.1708076641. The cubic root of 19928821 is about 271.1193630037.

The spelling of 19928821 in words is "nineteen million, nine hundred twenty-eight thousand, eight hundred twenty-one".