21505442 has 16 divisors (see below), whose sum is σ = 39035520. Its totient is φ = 8674368.

The previous prime is 21505417. The next prime is 21505447. The reversal of 21505442 is 24450512.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21505447) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 44942 + ... + 45417.

It is an arithmetic number, because the mean of its divisors is an integer number (2439720).

Almost surely, 2^21505442 is an apocalyptic number.

21505442 is a deficient number, since it is larger than the sum of its proper divisors (17530078).

21505442 is a wasteful number, since it uses less digits than its factorization.

21505442 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90385.

The product of its (nonzero) digits is 1600, while the sum is 23.

The square root of 21505442 is about 4637.3960365705. The cubic root of 21505442 is about 278.0883472635.

Adding to 21505442 its reverse (24450512), we get a palindrome (45955954).

The spelling of 21505442 in words is "twenty-one million, five hundred five thousand, four hundred forty-two".