21056545155973 has 2 divisors, whose sum is σ = 21056545155974. Its totient is φ = 21056545155972.

The previous prime is 21056545155967. The next prime is 21056545156021. The reversal of 21056545155973 is 37955154565012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13349830602564 + 7706714553409 = 3653742^2 + 2776097^2 .

It is a cyclic number.

It is not a de Polignac number, because 21056545155973 - 2⁵ = 21056545155941 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21056542155973) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10528272577986 + 10528272577987.

It is an arithmetic number, because the mean of its divisors is an integer number (10528272577987).

Almost surely, 2^{21056545155973} is an apocalyptic number.

It is an amenable number.

21056545155973 is a deficient number, since it is larger than the sum of its proper divisors (1).

21056545155973 is an equidigital number, since it uses as much as digits as its factorization.

21056545155973 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 28350000, while the sum is 58.

It can be divided in two parts, 2105654 and 5155973, that added together give a palindrome (7261627).

The spelling of 21056545155973 in words is "twenty-one trillion, fifty-six billion, five hundred forty-five million, one hundred fifty-five thousand, nine hundred seventy-three".