21251236250645 has 12 divisors (see below), whose sum is σ = 26914308073740. Its totient is φ = 16106200104384.

The previous prime is 21251236250627. The next prime is 21251236250653. The reversal of 21251236250645 is 54605263215212.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 12413262376516 + 8837973874129 = 3523246^2 + 2972873^2 .

It is not a de Polignac number, because 21251236250645 - 2³⁰ = 21250162508821 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21251236250596 and 21251236250605.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 5886767240 + ... + 5886770849.

It is an arithmetic number, because the mean of its divisors is an integer number (2242859006145).

Almost surely, 2^{21251236250645} is an apocalyptic number.

It is an amenable number.

21251236250645 is a deficient number, since it is larger than the sum of its proper divisors (5663071823095).

21251236250645 is a wasteful number, since it uses less digits than its factorization.

21251236250645 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11773538132 (or 11773538113 counting only the distinct ones).

The product of its (nonzero) digits is 864000, while the sum is 44.

Adding to 21251236250645 its reverse (54605263215212), we get a palindrome (75856499465857).

The spelling of 21251236250645 in words is "twenty-one trillion, two hundred fifty-one billion, two hundred thirty-six million, two hundred fifty thousand, six hundred forty-five".