19965921 has 4 divisors (see below), whose sum is σ = 26621232. Its totient is φ = 13310612.

The previous prime is 19965919. The next prime is 19965937. The reversal of 19965921 is 12956991.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 12956991 = 3 ⋅4318997.

It is a cyclic number.

It is not a de Polignac number, because 19965921 - 2¹ = 19965919 is a prime.

It is not an unprimeable number, because it can be changed into a prime (19965961) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3327651 + ... + 3327656.

It is an arithmetic number, because the mean of its divisors is an integer number (6655308).

Almost surely, 2^19965921 is an apocalyptic number.

It is an amenable number.

19965921 is a deficient number, since it is larger than the sum of its proper divisors (6655311).

19965921 is an equidigital number, since it uses as much as digits as its factorization.

19965921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6655310.

The product of its digits is 43740, while the sum is 42.

The square root of 19965921 is about 4468.3241825096. The cubic root of 19965921 is about 271.2874996114.

The spelling of 19965921 in words is "nineteen million, nine hundred sixty-five thousand, nine hundred twenty-one".