1661209560 has 160 divisors (see below), whose sum is σ = 5603994000. Its totient is φ = 441365760.

The previous prime is 1661209531. The next prime is 1661209567. The reversal of 1661209560 is 659021661.

1661209560 is a `hidden beast` number, since 16 + 61 + 20 + 9 + 560 = 666.

It is a hoax number, since the sum of its digits (36) coincides with the sum of the digits of its distinct prime factors.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661209567) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 1071666 + ... + 1073214.

Almost surely, 2^1661209560 is an apocalyptic number.

1661209560 is a gapful number since it is divisible by the number (10) 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 1661209560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2801997000).

1661209560 is an abundant number, since it is smaller than the sum of its proper divisors (3942784440).

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

1661209560 is a wasteful number, since it uses less digits than its factorization.

1661209560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1903 (or 1890 counting only the distinct ones).

The product of its (nonzero) digits is 19440, while the sum is 36.

The square root of 1661209560 is about 40757.9386132321. The cubic root of 1661209560 is about 1184.3356635200.

The spelling of 1661209560 in words is "one billion, six hundred sixty-one million, two hundred nine thousand, five hundred sixty".