660921553 has 4 divisors (see below), whose sum is σ = 660978688. Its totient is φ = 660864420.

The previous prime is 660921551. The next prime is 660921587. The reversal of 660921553 is 355129066.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 660921553 - 2¹ = 660921551 is a prime.

It is a super-3 number, since 3×660921553³ (a number of 27 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (660921551) 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, 4401 + ... + 36622.

It is an arithmetic number, because the mean of its divisors is an integer number (165244672).

Almost surely, 2^660921553 is an apocalyptic number.

It is an amenable number.

660921553 is a deficient number, since it is larger than the sum of its proper divisors (57135).

660921553 is a wasteful number, since it uses less digits than its factorization.

660921553 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 57134.

The product of its (nonzero) digits is 48600, while the sum is 37.

The square root of 660921553 is about 25708.3946017638. The cubic root of 660921553 is about 871.0638120708.

The spelling of 660921553 in words is "six hundred sixty million, nine hundred twenty-one thousand, five hundred fifty-three".