21721443325 has 12 divisors (see below), whose sum is σ = 26937599668. Its totient is φ = 17375212800.

The previous prime is 21721443313. The next prime is 21721443353. The reversal of 21721443325 is 52334412712.

It can be written as a sum of positive squares in 6 ways, for example, as 611968644 + 21109474681 = 24738^2 + 145291^2 .

It is not a de Polignac number, because 21721443325 - 2¹¹ = 21721441277 is a prime.

It is a super-2 number, since 2×21721443325² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

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, 205765 + ... + 292885.

Almost surely, 2^21721443325 is an apocalyptic number.

21721443325 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21721443325 is a deficient number, since it is larger than the sum of its proper divisors (5216156343).

21721443325 is an equidigital number, since it uses as much as digits as its factorization.

21721443325 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 97104 (or 97099 counting only the distinct ones).

The product of its digits is 40320, while the sum is 34.

The spelling of 21721443325 in words is "twenty-one billion, seven hundred twenty-one million, four hundred forty-three thousand, three hundred twenty-five".