19712921 has 4 divisors (see below), whose sum is σ = 19723812. Its totient is φ = 19702032.

The previous prime is 19712879. The next prime is 19712933. The reversal of 19712921 is 12921791.

19712921 = 3139² + 3140².

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in 2 ways, for example, as 9859600 + 9853321 = 3140^2 + 3139^2 .

It is a cyclic number.

It is not a de Polignac number, because 19712921 - 2⁶ = 19712857 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19712951) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2006 + ... + 6591.

It is an arithmetic number, because the mean of its divisors is an integer number (4930953).

Almost surely, 2^19712921 is an apocalyptic number.

19712921 is the 3140-th centered square number.

It is an amenable number.

19712921 is a deficient number, since it is larger than the sum of its proper divisors (10891).

19712921 is an equidigital number, since it uses as much as digits as its factorization.

19712921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10890.

The product of its digits is 2268, while the sum is 32.

The square root of 19712921 is about 4439.9235353776. The cubic root of 19712921 is about 270.1367437192.

The spelling of 19712921 in words is "nineteen million, seven hundred twelve thousand, nine hundred twenty-one".