19666950021 has 12 divisors (see below), whose sum is σ = 30078864972. Its totient is φ = 12340046976.

The previous prime is 19666950019. The next prime is 19666950031. The reversal of 19666950021 is 12005966691.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 5385504996 + 14281445025 = 73386^2 + 119505^2 .

It is not a de Polignac number, because 19666950021 - 2¹ = 19666950019 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19666950031) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 64270926 + ... + 64271231.

It is an arithmetic number, because the mean of its divisors is an integer number (2506572081).

Almost surely, 2^19666950021 is an apocalyptic number.

It is an amenable number.

19666950021 is a deficient number, since it is larger than the sum of its proper divisors (10411914951).

19666950021 is a wasteful number, since it uses less digits than its factorization.

19666950021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128542180 (or 128542177 counting only the distinct ones).

The product of its (nonzero) digits is 174960, while the sum is 45.

The spelling of 19666950021 in words is "nineteen billion, six hundred sixty-six million, nine hundred fifty thousand, twenty-one".