21231641605 has 4 divisors (see below), whose sum is σ = 25477969932. Its totient is φ = 16985313280.

The previous prime is 21231641567. The next prime is 21231641609. The reversal of 21231641605 is 50614613212.

It is a happy number.

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 2948815809 + 18282825796 = 54303^2 + 135214^2 .

It is not a de Polignac number, because 21231641605 - 2¹³ = 21231633413 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21231641609) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2123164156 + ... + 2123164165.

It is an arithmetic number, because the mean of its divisors is an integer number (6369492483).

Almost surely, 2^21231641605 is an apocalyptic number.

It is an amenable number.

21231641605 is a deficient number, since it is larger than the sum of its proper divisors (4246328327).

21231641605 is an equidigital number, since it uses as much as digits as its factorization.

21231641605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4246328326.

The product of its (nonzero) digits is 8640, while the sum is 31.

The spelling of 21231641605 in words is "twenty-one billion, two hundred thirty-one million, six hundred forty-one thousand, six hundred five".