661465440 has 336 divisors, whose sum is σ = 2409514128. Its totient is φ = 171445248.

The previous prime is 661465433. The next prime is 661465447. The reversal of 661465440 is 44564166.

It is an interprime number because it is at equal distance from previous prime (661465433) and next prime (661465447).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a junction number, because it is equal to n+sod(n) for n = 661465395 and 661465404.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (661465447) by changing a digit.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 6181867 + ... + 6181973.

It is an arithmetic number, because the mean of its divisors is an integer number (7171173).

Almost surely, 2^661465440 is an apocalyptic number.

661465440 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 661465440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1204757064).

661465440 is an abundant number, since it is smaller than the sum of its proper divisors (1748048688).

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

661465440 is a wasteful number, since it uses less digits than its factorization.

661465440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193 (or 170 counting only the distinct ones).

The product of its (nonzero) digits is 69120, while the sum is 36.

The square root of 661465440 is about 25718.9704304041. The cubic root of 661465440 is about 871.3026857994.

The spelling of 661465440 in words is "six hundred sixty-one million, four hundred sixty-five thousand, four hundred forty".