661386240 has 264 divisors, whose sum is σ = 2370720768. Its totient is φ = 170311680.

The previous prime is 661386233. The next prime is 661386259. The reversal of 661386240 is 42683166.

It is a super-2 number, since 2×661386240² = 874863516922675200, which contains 22 as substring.

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 = 661386195 and 661386204.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 1428249 + ... + 1428711.

Almost surely, 2^661386240 is an apocalyptic number.

661386240 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 661386240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1185360384).

661386240 is an abundant number, since it is smaller than the sum of its proper divisors (1709334528).

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

661386240 is a wasteful number, since it uses less digits than its factorization.

661386240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 525 (or 504 counting only the distinct ones).

The product of its (nonzero) digits is 41472, while the sum is 36.

The square root of 661386240 is about 25717.4306648234. The cubic root of 661386240 is about 871.2679095169.

The spelling of 661386240 in words is "six hundred sixty-one million, three hundred eighty-six thousand, two hundred forty".