21689288641 has 4 divisors (see below), whose sum is σ = 21689642884. Its totient is φ = 21688934400.

The previous prime is 21689288597. The next prime is 21689288651. The reversal of 21689288641 is 14688298612.

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 15253238016 + 6436050625 = 123504^2 + 80225^2 .

It is a cyclic number.

It is not a de Polignac number, because 21689288641 - 2⁷ = 21689288513 is a prime.

It is a super-2 number, since 2×21689288641² (a number of 21 digits) contains 22 as substring.

It is a deceptive number, since it divides R_21689288640.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21689288651) 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, 59040 + ... + 216481.

It is an arithmetic number, because the mean of its divisors is an integer number (5422410721).

Almost surely, 2^21689288641 is an apocalyptic number.

21689288641 is the 78721-st nonagonal number.

It is an amenable number.

21689288641 is a deficient number, since it is larger than the sum of its proper divisors (354243).

21689288641 is an equidigital number, since it uses as much as digits as its factorization.

21689288641 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 354242.

The product of its digits is 2654208, while the sum is 55.

The spelling of 21689288641 in words is "twenty-one billion, six hundred eighty-nine million, two hundred eighty-eight thousand, six hundred forty-one".