21251473042 has 4 divisors (see below), whose sum is σ = 31877209566. Its totient is φ = 10625736520.

The previous prime is 21251473013. The next prime is 21251473049. The reversal of 21251473042 is 24037415212.

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., 15250027081 + 6001445961 = 123491^2 + 77469^2 .

It is a junction number, because it is equal to n+sod(n) for n = 21251472995 and 21251473013.

It is not an unprimeable number, because it can be changed into a prime (21251473049) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5312868259 + ... + 5312868262.

Almost surely, 2^21251473042 is an apocalyptic number.

21251473042 is a deficient number, since it is larger than the sum of its proper divisors (10625736524).

21251473042 is a wasteful number, since it uses less digits than its factorization.

21251473042 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10625736523.

The product of its (nonzero) digits is 13440, while the sum is 31.

Adding to 21251473042 its reverse (24037415212), we get a palindrome (45288888254).

The spelling of 21251473042 in words is "twenty-one billion, two hundred fifty-one million, four hundred seventy-three thousand, forty-two".