21226537661 has 4 divisors (see below), whose sum is σ = 24258900192. Its totient is φ = 18194175132.

The previous prime is 21226537583. The next prime is 21226537669. The reversal of 21226537661 is 16673562212.

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 not a de Polignac number, because 21226537661 - 2³⁴ = 4046668477 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 (21226537669) 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, 1516181255 + ... + 1516181268.

It is an arithmetic number, because the mean of its divisors is an integer number (6064725048).

Almost surely, 2^21226537661 is an apocalyptic number.

It is an amenable number.

21226537661 is a deficient number, since it is larger than the sum of its proper divisors (3032362531).

21226537661 is an equidigital number, since it uses as much as digits as its factorization.

21226537661 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3032362530.

The product of its digits is 181440, while the sum is 41.

The spelling of 21226537661 in words is "twenty-one billion, two hundred twenty-six million, five hundred thirty-seven thousand, six hundred sixty-one".