661637 has 8 divisors (see below), whose sum is σ = 705600. Its totient is φ = 618624.

The previous prime is 661621. The next prime is 661663. The reversal of 661637 is 736166.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 661637 - 2⁴ = 661621 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661607) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1664 + ... + 2022.

It is an arithmetic number, because the mean of its divisors is an integer number (88200).

2⁶⁶¹⁶³⁷ is an apocalyptic number.

It is an amenable number.

661637 is a deficient number, since it is larger than the sum of its proper divisors (43963).

661637 is a wasteful number, since it uses less digits than its factorization.

661637 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 475.

The product of its digits is 4536, while the sum is 29.

The square root of 661637 is about 813.4107203621. The cubic root of 661637 is about 87.1378007330.

Subtracting 661637 from its reverse (736166), we obtain a square (74529 = 273²).

The spelling of 661637 in words is "six hundred sixty-one thousand, six hundred thirty-seven".