21641603525 has 6 divisors (see below), whose sum is σ = 26835588402. Its totient is φ = 17313282800.

The previous prime is 21641603521. The next prime is 21641603561. The reversal of 21641603525 is 52530614612.

It can be written as a sum of positive squares in 3 ways, for example, as 14371681 + 21627231844 = 3791^2 + 147062^2 .

It is not a de Polignac number, because 21641603525 - 2² = 21641603521 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21641603521) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 432832046 + ... + 432832095.

It is an arithmetic number, because the mean of its divisors is an integer number (4472598067).

Almost surely, 2^21641603525 is an apocalyptic number.

21641603525 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21641603525 is a deficient number, since it is larger than the sum of its proper divisors (5193984877).

21641603525 is an equidigital number, since it uses as much as digits as its factorization.

21641603525 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 865664151 (or 865664146 counting only the distinct ones).

The product of its (nonzero) digits is 43200, while the sum is 35.

The spelling of 21641603525 in words is "twenty-one billion, six hundred forty-one million, six hundred three thousand, five hundred twenty-five".