21730042 has 4 divisors (see below), whose sum is σ = 32595066. Its totient is φ = 10865020.

The previous prime is 21730031. The next prime is 21730057. The reversal of 21730042 is 24003712.

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., 18671041 + 3059001 = 4321^2 + 1749^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5432509 + ... + 5432512.

Almost surely, 2^21730042 is an apocalyptic number.

21730042 is a deficient number, since it is larger than the sum of its proper divisors (10865024).

21730042 is a wasteful number, since it uses less digits than its factorization.

21730042 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10865023.

The product of its (nonzero) digits is 336, while the sum is 19.

The square root of 21730042 is about 4661.5493132649. The cubic root of 21730042 is about 279.0531024337.

Adding to 21730042 its reverse (24003712), we get a palindrome (45733754).

The spelling of 21730042 in words is "twenty-one million, seven hundred thirty thousand, forty-two".