21251234645 has 8 divisors (see below), whose sum is σ = 25502280504. Its totient is φ = 17000455104.

The previous prime is 21251234639. The next prime is 21251234647. The reversal of 21251234645 is 54643215212.

It can be written as a sum of positive squares in 4 ways, for example, as 10504081 + 21240730564 = 3241^2 + 145742^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21251234645 - 2⁶ = 21251234581 is a prime.

It is a super-2 number, since 2×21251234645² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21251234647) 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, 225347 + ... + 305423.

It is an arithmetic number, because the mean of its divisors is an integer number (3187785063).

Almost surely, 2^21251234645 is an apocalyptic number.

It is an amenable number.

21251234645 is a deficient number, since it is larger than the sum of its proper divisors (4251045859).

21251234645 is an equidigital number, since it uses as much as digits as its factorization.

21251234645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 133159.

The product of its digits is 57600, while the sum is 35.

Adding to 21251234645 its reverse (54643215212), we get a palindrome (75894449857).

The spelling of 21251234645 in words is "twenty-one billion, two hundred fifty-one million, two hundred thirty-four thousand, six hundred forty-five".