21009138369397 has 2 divisors, whose sum is σ = 21009138369398. Its totient is φ = 21009138369396.

The previous prime is 21009138369391. The next prime is 21009138369403. The reversal of 21009138369397 is 79396383190012.

It is a balanced prime because it is at equal distance from previous prime (21009138369391) and next prime (21009138369403).

It can be written as a sum of positive squares in only one way, i.e., 11446948955556 + 9562189413841 = 3383334^2 + 3092279^2 .

It is a cyclic number.

It is not a de Polignac number, because 21009138369397 - 2¹⁵ = 21009138336629 is a prime.

It is a super-2 number, since 2×21009138369397² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21009138369391) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10504569184698 + 10504569184699.

It is an arithmetic number, because the mean of its divisors is an integer number (10504569184699).

Almost surely, 2^{21009138369397} is an apocalyptic number.

It is an amenable number.

21009138369397 is a deficient number, since it is larger than the sum of its proper divisors (1).

21009138369397 is an equidigital number, since it uses as much as digits as its factorization.

21009138369397 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13226976, while the sum is 61.

The spelling of 21009138369397 in words is "twenty-one trillion, nine billion, one hundred thirty-eight million, three hundred sixty-nine thousand, three hundred ninety-seven".