21187237025 has 6 divisors (see below), whose sum is σ = 26272173942. Its totient is φ = 16949789600.

The previous prime is 21187237013. The next prime is 21187237031. The reversal of 21187237025 is 52073278112.

It can be written as a sum of positive squares in 3 ways, for example, as 1852321 + 21185384704 = 1361^2 + 145552^2 .

It is not a de Polignac number, because 21187237025 - 2⁸ = 21187236769 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21187237025.

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 in 5 ways as a sum of consecutive naturals, for example, 423744716 + ... + 423744765.

It is an arithmetic number, because the mean of its divisors is an integer number (4378695657).

Almost surely, 2^21187237025 is an apocalyptic number.

21187237025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21187237025 is a deficient number, since it is larger than the sum of its proper divisors (5084936917).

21187237025 is an equidigital number, since it uses as much as digits as its factorization.

21187237025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 847489491 (or 847489486 counting only the distinct ones).

The product of its (nonzero) digits is 47040, while the sum is 38.

The spelling of 21187237025 in words is "twenty-one billion, one hundred eighty-seven million, two hundred thirty-seven thousand, twenty-five".