651640 has 32 divisors (see below), whose sum is σ = 1600560. Its totient is φ = 236800.

The previous prime is 651617. The next prime is 651641. The reversal of 651640 is 46156.

It is a Harshad number since it is a multiple of its sum of digits (22).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (651641) by changing a digit.

651640 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 301 + ... + 1180.

2⁶⁵¹⁶⁴⁰ is an apocalyptic number.

It is an amenable number.

651640 is an abundant number, since it is smaller than the sum of its proper divisors (948920).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

651640 is a wasteful number, since it uses less digits than its factorization.

651640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1503 (or 1499 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 651640 is about 807.2422189157. The cubic root of 651640 is about 86.6967022785.

Adding to 651640 its reverse (46156), we get a palindrome (697796).

It can be divided in two parts, 6516 and 40, that added together give a palindrome (6556).

The spelling of 651640 in words is "six hundred fifty-one thousand, six hundred forty".