21725256647 has 2 divisors, whose sum is σ = 21725256648. Its totient is φ = 21725256646.

The previous prime is 21725256643. The next prime is 21725256673. The reversal of 21725256647 is 74665252712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21725256647 - 2² = 21725256643 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21725256643) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10862628323 + 10862628324.

It is an arithmetic number, because the mean of its divisors is an integer number (10862628324).

Almost surely, 2^21725256647 is an apocalyptic number.

21725256647 is a deficient number, since it is larger than the sum of its proper divisors (1).

21725256647 is an equidigital number, since it uses as much as digits as its factorization.

21725256647 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1411200, while the sum is 47.

The spelling of 21725256647 in words is "twenty-one billion, seven hundred twenty-five million, two hundred fifty-six thousand, six hundred forty-seven".