21387856297 has 2 divisors, whose sum is σ = 21387856298. Its totient is φ = 21387856296.

The previous prime is 21387856229. The next prime is 21387856307. The reversal of 21387856297 is 79265878312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19375526416 + 2012329881 = 139196^2 + 44859^2 .

It is a cyclic number.

It is not a de Polignac number, because 21387856297 - 2¹¹ = 21387854249 is a prime.

It is a super-2 number, since 2×21387856297² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21387856397) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10693928148 + 10693928149.

It is an arithmetic number, because the mean of its divisors is an integer number (10693928149).

Almost surely, 2^21387856297 is an apocalyptic number.

It is an amenable number.

21387856297 is a deficient number, since it is larger than the sum of its proper divisors (1).

21387856297 is an equidigital number, since it uses as much as digits as its factorization.

21387856297 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10160640, while the sum is 58.

The spelling of 21387856297 in words is "twenty-one billion, three hundred eighty-seven million, eight hundred fifty-six thousand, two hundred ninety-seven".