21561811607 has 16 divisors (see below), whose sum is σ = 24722107200. Its totient is φ = 18421624320.

The previous prime is 21561811573. The next prime is 21561811613. The reversal of 21561811607 is 70611816512.

It is a cyclic number.

It is not a de Polignac number, because 21561811607 - 2⁶ = 21561811543 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561811907) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3135569 + ... + 3142437.

It is an arithmetic number, because the mean of its divisors is an integer number (1545131700).

Almost surely, 2^21561811607 is an apocalyptic number.

21561811607 is a deficient number, since it is larger than the sum of its proper divisors (3160295593).

21561811607 is an equidigital number, since it uses as much as digits as its factorization.

21561811607 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8266.

The product of its (nonzero) digits is 20160, while the sum is 38.

The spelling of 21561811607 in words is "twenty-one billion, five hundred sixty-one million, eight hundred eleven thousand, six hundred seven".