21138905641 has 4 divisors (see below), whose sum is σ = 24158749312. Its totient is φ = 18119061972.

The previous prime is 21138905617. The next prime is 21138905647. The reversal of 21138905641 is 14650983112.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21138905641 - 2¹³ = 21138897449 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21138905594 and 21138905603.

It is not an unprimeable number, because it can be changed into a prime (21138905647) 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, 1509921825 + ... + 1509921838.

It is an arithmetic number, because the mean of its divisors is an integer number (6039687328).

Almost surely, 2^21138905641 is an apocalyptic number.

It is an amenable number.

21138905641 is a deficient number, since it is larger than the sum of its proper divisors (3019843671).

21138905641 is an equidigital number, since it uses as much as digits as its factorization.

21138905641 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3019843670.

The product of its (nonzero) digits is 51840, while the sum is 40.

The spelling of 21138905641 in words is "twenty-one billion, one hundred thirty-eight million, nine hundred five thousand, six hundred forty-one".