20981897647 has 2 divisors, whose sum is σ = 20981897648. Its totient is φ = 20981897646.

The previous prime is 20981897551. The next prime is 20981897653. The reversal of 20981897647 is 74679818902.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 20981897647 - 2³¹ = 18834413999 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20981897047) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10490948823 + 10490948824.

It is an arithmetic number, because the mean of its divisors is an integer number (10490948824).

Almost surely, 2^20981897647 is an apocalyptic number.

20981897647 is a deficient number, since it is larger than the sum of its proper divisors (1).

20981897647 is an equidigital number, since it uses as much as digits as its factorization.

20981897647 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12192768, while the sum is 61.

The spelling of 20981897647 in words is "twenty billion, nine hundred eighty-one million, eight hundred ninety-seven thousand, six hundred forty-seven".