1561780 has 48 divisors (see below), whose sum is σ = 3709440. Its totient is φ = 547200.

The previous prime is 1561759. The next prime is 1561801. The reversal of 1561780 is 871651.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (1561759) and next prime (1561801).

It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.

It is a nialpdrome in base 11.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 6706 + ... + 6934.

It is an arithmetic number, because the mean of its divisors is an integer number (77280).

2^1561780 is an apocalyptic number.

1561780 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 1561780, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1854720).

1561780 is an abundant number, since it is smaller than the sum of its proper divisors (2147660).

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

1561780 is a wasteful number, since it uses less digits than its factorization.

1561780 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 280 (or 278 counting only the distinct ones).

The product of its (nonzero) digits is 1680, while the sum is 28.

The square root of 1561780 is about 1249.7119668148. The cubic root of 1561780 is about 116.0218944008.

It can be divided in two parts, 1561 and 780, that multiplied together give a triangular number (1217580 = T₁₅₆₀).

The spelling of 1561780 in words is "one million, five hundred sixty-one thousand, seven hundred eighty".