661988 has 12 divisors (see below), whose sum is σ = 1166592. Its totient is φ = 328680.

The previous prime is 661987. The next prime is 661993. The reversal of 661988 is 889166.

It is a super-2 number, since 2×661988² = 876456224288, which contains 22 as substring.

It is a plaindrome in base 14.

It is not an unprimeable number, because it can be changed into a prime (661987) 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, 173 + ... + 1163.

It is an arithmetic number, because the mean of its divisors is an integer number (97216).

2⁶⁶¹⁹⁸⁸ is an apocalyptic number.

It is an amenable number.

661988 is a deficient number, since it is larger than the sum of its proper divisors (504604).

661988 is a wasteful number, since it uses less digits than its factorization.

661988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1162 (or 1160 counting only the distinct ones).

The product of its digits is 20736, while the sum is 38.

The square root of 661988 is about 813.6264499142. The cubic root of 661988 is about 87.1532069457.

The spelling of 661988 in words is "six hundred sixty-one thousand, nine hundred eighty-eight".