21123542020345 has 4 divisors (see below), whose sum is σ = 25348250424420. Its totient is φ = 16898833616272.

The previous prime is 21123542020337. The next prime is 21123542020349. The reversal of 21123542020345 is 54302024532112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 15086535771321 + 6037006249024 = 3884139^2 + 2457032^2 .

It is a cyclic number.

It is not a de Polignac number, because 21123542020345 - 2³ = 21123542020337 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21123542020345.

It is not an unprimeable number, because it can be changed into a prime (21123542020349) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2112354202030 + ... + 2112354202039.

It is an arithmetic number, because the mean of its divisors is an integer number (6337062606105).

Almost surely, 2^{21123542020345} is an apocalyptic number.

It is an amenable number.

21123542020345 is a deficient number, since it is larger than the sum of its proper divisors (4224708404075).

21123542020345 is an equidigital number, since it uses as much as digits as its factorization.

21123542020345 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4224708404074.

The product of its (nonzero) digits is 57600, while the sum is 34.

Adding to 21123542020345 its reverse (54302024532112), we get a palindrome (75425566552457).

The spelling of 21123542020345 in words is "twenty-one trillion, one hundred twenty-three billion, five hundred forty-two million, twenty thousand, three hundred forty-five".