21277388581 has 4 divisors (see below), whose sum is σ = 22528999692. Its totient is φ = 20025777472.

The previous prime is 21277388551. The next prime is 21277388599. The reversal of 21277388581 is 18588377212.

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 17125648225 + 4151740356 = 130865^2 + 64434^2 .

It is a cyclic number.

It is not a de Polignac number, because 21277388581 - 2⁵ = 21277388549 is a prime.

It is a super-2 number, since 2×21277388581² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21277388551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 625805530 + ... + 625805563.

It is an arithmetic number, because the mean of its divisors is an integer number (5632249923).

Almost surely, 2^21277388581 is an apocalyptic number.

It is an amenable number.

21277388581 is a deficient number, since it is larger than the sum of its proper divisors (1251611111).

21277388581 is a wasteful number, since it uses less digits than its factorization.

21277388581 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1251611110.

The product of its digits is 1505280, while the sum is 52.

The spelling of 21277388581 in words is "twenty-one billion, two hundred seventy-seven million, three hundred eighty-eight thousand, five hundred eighty-one".