19421921 has 4 divisors (see below), whose sum is σ = 19430832. Its totient is φ = 19413012.

The previous prime is 19421911. The next prime is 19421953. The reversal of 19421921 is 12912491.

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 a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 12912491 = 421 ⋅30671.

It is a cyclic number.

It is not a de Polignac number, because 19421921 - 2¹⁰ = 19420897 is a prime.

It is a super-2 number, since 2×19421921² = 754422030660482, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (19421911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1250 + ... + 6356.

It is an arithmetic number, because the mean of its divisors is an integer number (4857708).

Almost surely, 2^19421921 is an apocalyptic number.

It is an amenable number.

19421921 is a deficient number, since it is larger than the sum of its proper divisors (8911).

19421921 is an equidigital number, since it uses as much as digits as its factorization.

19421921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8910.

The product of its digits is 1296, while the sum is 29.

The square root of 19421921 is about 4407.0308598874. The cubic root of 19421921 is about 268.8009057347.

The spelling of 19421921 in words is "nineteen million, four hundred twenty-one thousand, nine hundred twenty-one".