21155022397 has 2 divisors, whose sum is σ = 21155022398. Its totient is φ = 21155022396.

The previous prime is 21155022311. The next prime is 21155022407. The reversal of 21155022397 is 79322055112.

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., 14648018841 + 6507003556 = 121029^2 + 80666^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21155022397 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21155022197) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10577511198 + 10577511199.

It is an arithmetic number, because the mean of its divisors is an integer number (10577511199).

Almost surely, 2^21155022397 is an apocalyptic number.

It is an amenable number.

21155022397 is a deficient number, since it is larger than the sum of its proper divisors (1).

21155022397 is an equidigital number, since it uses as much as digits as its factorization.

21155022397 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 37800, while the sum is 37.

The spelling of 21155022397 in words is "twenty-one billion, one hundred fifty-five million, twenty-two thousand, three hundred ninety-seven".