21563638904025 has 18 divisors (see below), whose sum is σ = 38622873237390. Its totient is φ = 11500607415360.

The previous prime is 21563638904009. The next prime is 21563638904069. The reversal of 21563638904025 is 52040983636512.

It is a happy number.

21563638904025 is a `hidden beast` number, since 2 + 1 + 563 + 6 + 38 + 9 + 0 + 40 + 2 + 5 = 666.

It can be written as a sum of positive squares in 3 ways, for example, as 2857252696281 + 18706386207744 = 1690341^2 + 4325088^2 .

It is not a de Polignac number, because 21563638904025 - 2⁴ = 21563638904009 is a prime.

It is a super-2 number, since 2×21563638904025² (a number of 27 digits) contains 22 as substring.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 47919197340 + ... + 47919197789.

It is an arithmetic number, because the mean of its divisors is an integer number (2145715179855).

Almost surely, 2^{21563638904025} is an apocalyptic number.

21563638904025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21563638904025 is a deficient number, since it is larger than the sum of its proper divisors (17059234333365).

21563638904025 is a wasteful number, since it uses less digits than its factorization.

21563638904025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 95838395145 (or 95838395137 counting only the distinct ones).

The product of its (nonzero) digits is 9331200, while the sum is 54.

The spelling of 21563638904025 in words is "twenty-one trillion, five hundred sixty-three billion, six hundred thirty-eight million, nine hundred four thousand, twenty-five".