21551671507 has 4 divisors (see below), whose sum is σ = 21576079720. Its totient is φ = 21527263296.

The previous prime is 21551671457. The next prime is 21551671517. The reversal of 21551671507 is 70517615512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21551671507 - 2²⁷ = 21417453779 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21551671507.

It is not an unprimeable number, because it can be changed into a prime (21551671517) 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, 12202782 + ... + 12204547.

It is an arithmetic number, because the mean of its divisors is an integer number (5394019930).

Almost surely, 2^21551671507 is an apocalyptic number.

21551671507 is a deficient number, since it is larger than the sum of its proper divisors (24408213).

21551671507 is an equidigital number, since it uses as much as digits as its factorization.

21551671507 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 24408212.

The product of its (nonzero) digits is 73500, while the sum is 40.

The spelling of 21551671507 in words is "twenty-one billion, five hundred fifty-one million, six hundred seventy-one thousand, five hundred seven".