21291656909 has 8 divisors (see below), whose sum is σ = 21586626432. Its totient is φ = 20996776800.

The previous prime is 21291656891. The next prime is 21291656941. The reversal of 21291656909 is 90965619212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21291656909 - 2¹² = 21291652813 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21291656999) 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 7 ways as a sum of consecutive naturals, for example, 562082 + ... + 598764.

It is an arithmetic number, because the mean of its divisors is an integer number (2698328304).

Almost surely, 2^21291656909 is an apocalyptic number.

It is an amenable number.

21291656909 is a deficient number, since it is larger than the sum of its proper divisors (294969523).

21291656909 is an equidigital number, since it uses as much as digits as its factorization.

21291656909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 44707.

The product of its (nonzero) digits is 524880, while the sum is 50.

The spelling of 21291656909 in words is "twenty-one billion, two hundred ninety-one million, six hundred fifty-six thousand, nine hundred nine".