21013431242 has 4 divisors (see below), whose sum is σ = 31520146866. Its totient is φ = 10506715620.

The previous prime is 21013431239. The next prime is 21013431259. The reversal of 21013431242 is 24213431012.

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., 20147247481 + 866183761 = 141941^2 + 29431^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5253357809 + ... + 5253357812.

Almost surely, 2^21013431242 is an apocalyptic number.

21013431242 is a deficient number, since it is larger than the sum of its proper divisors (10506715624).

21013431242 is a wasteful number, since it uses less digits than its factorization.

21013431242 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10506715623.

The product of its (nonzero) digits is 1152, while the sum is 23.

Adding to 21013431242 its reverse (24213431012), we get a palindrome (45226862254).

It can be divided in two parts, 2101 and 3431242, that added together give a palindrome (3433343).

The spelling of 21013431242 in words is "twenty-one billion, thirteen million, four hundred thirty-one thousand, two hundred forty-two".