661821464 has 16 divisors (see below), whose sum is σ = 1247154000. Its totient is φ = 329247072.

The previous prime is 661821463. The next prime is 661821493. The reversal of 661821464 is 464128166.

It is a super-2 number, since 2×661821464² = 876015300422206592, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661821463) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 206267 + ... + 209450.

It is an arithmetic number, because the mean of its divisors is an integer number (77947125).

Almost surely, 2^661821464 is an apocalyptic number.

It is an amenable number.

661821464 is a deficient number, since it is larger than the sum of its proper divisors (585332536).

661821464 is a wasteful number, since it uses less digits than its factorization.

661821464 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 415922 (or 415918 counting only the distinct ones).

The product of its digits is 55296, while the sum is 38.

The square root of 661821464 is about 25725.8909272352. The cubic root of 661821464 is about 871.4589796942.

It can be divided in two parts, 6618 and 21464, that added together give a palindrome (28082).

The spelling of 661821464 in words is "six hundred sixty-one million, eight hundred twenty-one thousand, four hundred sixty-four".