661012440 has 128 divisors (see below), whose sum is σ = 2169573120. Its totient is φ = 159782400.

The previous prime is 661012427. The next prime is 661012463. The reversal of 661012440 is 44210166.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is a self number, because there is not a number n which added to its sum of digits gives 661012440.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 753282 + ... + 754158.

It is an arithmetic number, because the mean of its divisors is an integer number (16949790).

Almost surely, 2^661012440 is an apocalyptic number.

661012440 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 661012440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1084786560).

661012440 is an abundant number, since it is smaller than the sum of its proper divisors (1508560680).

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

661012440 is a wasteful number, since it uses less digits than its factorization.

661012440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1473 (or 1469 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 24.

The square root of 661012440 is about 25710.1621931873. The cubic root of 661012440 is about 871.1037385178.

The spelling of 661012440 in words is "six hundred sixty-one million, twelve thousand, four hundred forty".