661431540 has 192 divisors, whose sum is σ = 2347849728. Its totient is φ = 135129600.

The previous prime is 661431509. The next prime is 661431559. The reversal of 661431540 is 45134166.

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 661431498 and 661431507.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 280647 + ... + 282993.

It is an arithmetic number, because the mean of its divisors is an integer number (12228384).

Almost surely, 2^661431540 is an apocalyptic number.

661431540 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 661431540, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1173924864).

661431540 is an abundant number, since it is smaller than the sum of its proper divisors (1686418188).

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

661431540 is a wasteful number, since it uses less digits than its factorization.

661431540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2438 (or 2436 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 30.

The square root of 661431540 is about 25718.3113753606. The cubic root of 661431540 is about 871.2878008365.

The spelling of 661431540 in words is "six hundred sixty-one million, four hundred thirty-one thousand, five hundred forty".