21147397897 has 2 divisors, whose sum is σ = 21147397898. Its totient is φ = 21147397896.

The previous prime is 21147397889. The next prime is 21147397919. The reversal of 21147397897 is 79879374112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21146685561 + 712336 = 145419^2 + 844^2 .

It is a cyclic number.

It is not a de Polignac number, because 21147397897 - 2³ = 21147397889 is a prime.

It is not a weakly prime, because it can be changed into another prime (21147391897) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10573698948 + 10573698949.

It is an arithmetic number, because the mean of its divisors is an integer number (10573698949).

Almost surely, 2^21147397897 is an apocalyptic number.

It is an amenable number.

21147397897 is a deficient number, since it is larger than the sum of its proper divisors (1).

21147397897 is an equidigital number, since it uses as much as digits as its factorization.

21147397897 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5334336, while the sum is 58.

The spelling of 21147397897 in words is "twenty-one billion, one hundred forty-seven million, three hundred ninety-seven thousand, eight hundred ninety-seven".