21641562261 has 48 divisors (see below), whose sum is σ = 35849661120. Its totient is φ = 12936309120.

The previous prime is 21641562223. The next prime is 21641562289. The reversal of 21641562261 is 16226514612.

21641562261 is a `hidden beast` number, since 2 + 1 + 641 + 5 + 6 + 2 + 2 + 6 + 1 = 666.

It is not a de Polignac number, because 21641562261 - 2¹⁵ = 21641529493 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21641562211) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 139675 + ... + 250583.

It is an arithmetic number, because the mean of its divisors is an integer number (746867940).

Almost surely, 2^21641562261 is an apocalyptic number.

It is an amenable number.

21641562261 is a deficient number, since it is larger than the sum of its proper divisors (14208098859).

21641562261 is a wasteful number, since it uses less digits than its factorization.

21641562261 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 111008 (or 110996 counting only the distinct ones).

The product of its digits is 34560, while the sum is 36.

The spelling of 21641562261 in words is "twenty-one billion, six hundred forty-one million, five hundred sixty-two thousand, two hundred sixty-one".