21005430442 has 4 divisors (see below), whose sum is σ = 31508145666. Its totient is φ = 10502715220.

The previous prime is 21005430437. The next prime is 21005430451. The reversal of 21005430442 is 24403450012.

It is a happy number.

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., 14825741121 + 6179689321 = 121761^2 + 78611^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5251357609 + ... + 5251357612.

Almost surely, 2^21005430442 is an apocalyptic number.

21005430442 is a deficient number, since it is larger than the sum of its proper divisors (10502715224).

21005430442 is a wasteful number, since it uses less digits than its factorization.

21005430442 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10502715223.

The product of its (nonzero) digits is 3840, while the sum is 25.

Adding to 21005430442 its reverse (24403450012), we get a palindrome (45408880454).

The spelling of 21005430442 in words is "twenty-one billion, five million, four hundred thirty thousand, four hundred forty-two".