19921438 has 4 divisors (see below), whose sum is σ = 29882160. Its totient is φ = 9960718.

The previous prime is 19921423. The next prime is 19921439. The reversal of 19921438 is 83412991.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 83412991 = 43 ⋅1939837.

It is a junction number, because it is equal to n+sod(n) for n = 19921397 and 19921406.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (19921439) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 4980358 + ... + 4980361.

It is an arithmetic number, because the mean of its divisors is an integer number (7470540).

Almost surely, 2^19921438 is an apocalyptic number.

19921438 is a deficient number, since it is larger than the sum of its proper divisors (9960722).

19921438 is an equidigital number, since it uses as much as digits as its factorization.

19921438 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9960721.

The product of its digits is 15552, while the sum is 37.

The square root of 19921438 is about 4463.3438137791. The cubic root of 19921438 is about 271.0858784757.

The spelling of 19921438 in words is "nineteen million, nine hundred twenty-one thousand, four hundred thirty-eight".