21000001978343 has 2 divisors, whose sum is σ = 21000001978344. Its totient is φ = 21000001978342.

The previous prime is 21000001978331. The next prime is 21000001978349. The reversal of 21000001978343 is 34387910000012.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21000001978343 - 2⁴ = 21000001978327 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21000001978297 and 21000001978306.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21000001978349) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10500000989171 + 10500000989172.

It is an arithmetic number, because the mean of its divisors is an integer number (10500000989172).

Almost surely, 2^{21000001978343} is an apocalyptic number.

21000001978343 is a deficient number, since it is larger than the sum of its proper divisors (1).

21000001978343 is an equidigital number, since it uses as much as digits as its factorization.

21000001978343 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 36288, while the sum is 38.

Adding to 21000001978343 its reverse (34387910000012), we get a palindrome (55387911978355).

The spelling of 21000001978343 in words is "twenty-one trillion, one million, nine hundred seventy-eight thousand, three hundred forty-three".