651440 has 40 divisors (see below), whose sum is σ = 1607040. Its totient is φ = 244736.

The previous prime is 651439. The next prime is 651461. The reversal of 651440 is 44156.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (40).

It is a Harshad number since it is a multiple of its sum of digits (20).

It is an Ulam number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 651440.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1121 + ... + 1599.

It is an arithmetic number, because the mean of its divisors is an integer number (40176).

2⁶⁵¹⁴⁴⁰ is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 651440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (803520).

651440 is an abundant number, since it is smaller than the sum of its proper divisors (955600).

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

651440 is a wasteful number, since it uses less digits than its factorization.

651440 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 509 (or 503 counting only the distinct ones).

The product of its (nonzero) digits is 480, while the sum is 20.

The square root of 651440 is about 807.1183308537. The cubic root of 651440 is about 86.6878317802.

Adding to 651440 its reverse (44156), we get a palindrome (695596).

The spelling of 651440 in words is "six hundred fifty-one thousand, four hundred forty".