21470646557 has 4 divisors (see below), whose sum is σ = 21471195900. Its totient is φ = 21470097216.

The previous prime is 21470646541. The next prime is 21470646563. The reversal of 21470646557 is 75564607412.

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 21267555556 + 203091001 = 145834^2 + 14251^2 .

It is a cyclic number.

It is not a de Polignac number, because 21470646557 - 2⁴ = 21470646541 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 (21470606557) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 211148 + ... + 295845.

It is an arithmetic number, because the mean of its divisors is an integer number (5367798975).

Almost surely, 2^21470646557 is an apocalyptic number.

It is an amenable number.

21470646557 is a deficient number, since it is larger than the sum of its proper divisors (549343).

21470646557 is an equidigital number, since it uses as much as digits as its factorization.

21470646557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 549342.

The product of its (nonzero) digits is 1411200, while the sum is 47.

The spelling of 21470646557 in words is "twenty-one billion, four hundred seventy million, six hundred forty-six thousand, five hundred fifty-seven".