660402221 has 4 divisors (see below), whose sum is σ = 661873500. Its totient is φ = 658930944.

The previous prime is 660402203. The next prime is 660402251. The reversal of 660402221 is 122204066.

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 336906025 + 323496196 = 18355^2 + 17986^2 .

It is a cyclic number.

It is not a de Polignac number, because 660402221 - 2⁶ = 660402157 is a prime.

It is a super-2 number, since 2×660402221² = 872262187003465682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (660402251) 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, 734966 + ... + 735863.

It is an arithmetic number, because the mean of its divisors is an integer number (165468375).

Almost surely, 2^660402221 is an apocalyptic number.

It is an amenable number.

660402221 is a deficient number, since it is larger than the sum of its proper divisors (1471279).

660402221 is a wasteful number, since it uses less digits than its factorization.

660402221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1471278.

The product of its (nonzero) digits is 1152, while the sum is 23.

The square root of 660402221 is about 25698.2921806100. The cubic root of 660402221 is about 870.8356004937.

Adding to 660402221 its reverse (122204066), we get a palindrome (782606287).

The spelling of 660402221 in words is "six hundred sixty million, four hundred two thousand, two hundred twenty-one".