661626331563 has 4 divisors (see below), whose sum is σ = 882168442088. Its totient is φ = 441084221040.

The previous prime is 661626331549. The next prime is 661626331573. The reversal of 661626331563 is 365133626166.

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

It is not a de Polignac number, because 661626331563 - 2¹⁰ = 661626330539 is a prime.

It is a super-4 number, since 4×661626331563⁴ (a number of 48 digits) contains 4444 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (661626331573) 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, 110271055258 + ... + 110271055263.

It is an arithmetic number, because the mean of its divisors is an integer number (220542110522).

Almost surely, 2^661626331563 is an apocalyptic number.

661626331563 is a deficient number, since it is larger than the sum of its proper divisors (220542110525).

661626331563 is a wasteful number, since it uses less digits than its factorization.

661626331563 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 220542110524.

The product of its digits is 2099520, while the sum is 48.

The spelling of 661626331563 in words is "six hundred sixty-one billion, six hundred twenty-six million, three hundred thirty-one thousand, five hundred sixty-three".