21891442 has 4 divisors (see below), whose sum is σ = 32837166. Its totient is φ = 10945720.

The previous prime is 21891437. The next prime is 21891449. The reversal of 21891442 is 24419812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 19900521 + 1990921 = 4461^2 + 1411^2 .

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (21891449) 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 as a sum of consecutive naturals, namely, 5472859 + ... + 5472862.

Almost surely, 2^21891442 is an apocalyptic number.

21891442 is a deficient number, since it is larger than the sum of its proper divisors (10945724).

21891442 is a wasteful number, since it uses less digits than its factorization.

21891442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10945723.

The product of its digits is 4608, while the sum is 31.

The square root of 21891442 is about 4678.8291270360. The cubic root of 21891442 is about 279.7422883856.

The spelling of 21891442 in words is "twenty-one million, eight hundred ninety-one thousand, four hundred forty-two".