19900021 has 8 divisors (see below), whose sum is σ = 20345600. Its totient is φ = 19459440.

The previous prime is 19900009. The next prime is 19900057. The reversal of 19900021 is 12000991.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 19900021 - 2⁵ = 19899989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 19899965 and 19900001.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19903021) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 7456 + ... + 9766.

It is an arithmetic number, because the mean of its divisors is an integer number (2543200).

Almost surely, 2^19900021 is an apocalyptic number.

It is an amenable number.

19900021 is a deficient number, since it is larger than the sum of its proper divisors (445579).

19900021 is a wasteful number, since it uses less digits than its factorization.

19900021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2499.

The product of its (nonzero) digits is 162, while the sum is 22.

The square root of 19900021 is about 4460.9439584016. The cubic root of 19900021 is about 270.9886979396.

The spelling of 19900021 in words is "nineteen million, nine hundred thousand, twenty-one".