21641245381 has 6 divisors (see below), whose sum is σ = 25174509990. Its totient is φ = 18549638856.

The previous prime is 21641245349. The next prime is 21641245453. The reversal of 21641245381 is 18354214612.

It can be written as a sum of positive squares in only one way, i.e., 21087396225 + 553849156 = 145215^2 + 23534^2 .

It is not a de Polignac number, because 21641245381 - 2⁵ = 21641245349 is a prime.

It is a super-2 number, since 2×21641245381² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21641245381.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21641245321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 220828986 + ... + 220829083.

It is an arithmetic number, because the mean of its divisors is an integer number (4195751665).

Almost surely, 2^21641245381 is an apocalyptic number.

It is an amenable number.

21641245381 is a deficient number, since it is larger than the sum of its proper divisors (3533264609).

21641245381 is an equidigital number, since it uses as much as digits as its factorization.

21641245381 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 441658083 (or 441658076 counting only the distinct ones).

The product of its digits is 46080, while the sum is 37.

Adding to 21641245381 its reverse (18354214612), we get a palindrome (39995459993).

The spelling of 21641245381 in words is "twenty-one billion, six hundred forty-one million, two hundred forty-five thousand, three hundred eighty-one".