21034857271781 has 2 divisors, whose sum is σ = 21034857271782. Its totient is φ = 21034857271780.

The previous prime is 21034857271759. The next prime is 21034857272017. The reversal of 21034857271781 is 18717275843012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13700732102500 + 7334125169281 = 3701450^2 + 2708159^2 .

It is a cyclic number.

It is not a de Polignac number, because 21034857271781 - 2²² = 21034853077477 is a prime.

It is a super-2 number, since 2×21034857271781² (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 (21034850271781) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10517428635890 + 10517428635891.

It is an arithmetic number, because the mean of its divisors is an integer number (10517428635891).

Almost surely, 2^{21034857271781} is an apocalyptic number.

It is an amenable number.

21034857271781 is a deficient number, since it is larger than the sum of its proper divisors (1).

21034857271781 is an equidigital number, since it uses as much as digits as its factorization.

21034857271781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 5268480, while the sum is 56.

The spelling of 21034857271781 in words is "twenty-one trillion, thirty-four billion, eight hundred fifty-seven million, two hundred seventy-one thousand, seven hundred eighty-one".