15661540 has 12 divisors (see below), whose sum is σ = 32889276. Its totient is φ = 6264608.

The previous prime is 15661507. The next prime is 15661543. The reversal of 15661540 is 4516651.

It can be written as a sum of positive squares in 2 ways, for example, as 2643876 + 13017664 = 1626^2 + 3608^2 .

It is a junction number, because it is equal to n+sod(n) for n = 15661499 and 15661508.

It is not an unprimeable number, because it can be changed into a prime (15661543) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 391519 + ... + 391558.

It is an arithmetic number, because the mean of its divisors is an integer number (2740773).

Almost surely, 2^15661540 is an apocalyptic number.

15661540 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

15661540 is an abundant number, since it is smaller than the sum of its proper divisors (17227736).

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

15661540 is a wasteful number, since it uses less digits than its factorization.

15661540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 783086 (or 783084 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 28.

The square root of 15661540 is about 3957.4663611963. The cubic root of 15661540 is about 250.1947282842.

The spelling of 15661540 in words is "fifteen million, six hundred sixty-one thousand, five hundred forty".