1561778400 has 288 divisors, whose sum is σ = 6257599488. Its totient is φ = 329472000.

The previous prime is 1561778377. The next prime is 1561778417. The reversal of 1561778400 is 48771651.

It is a Harshad number since it is a multiple of its sum of digits (39).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 214825 + ... + 221975.

It is an arithmetic number, because the mean of its divisors is an integer number (21727776).

Almost surely, 2^1561778400 is an apocalyptic number.

1561778400 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 1561778400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3128799744).

1561778400 is an abundant number, since it is smaller than the sum of its proper divisors (4695821088).

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

1561778400 is a wasteful number, since it uses less digits than its factorization.

1561778400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7194 (or 7181 counting only the distinct ones).

The product of its (nonzero) digits is 47040, while the sum is 39.

The square root of 1561778400 is about 39519.3420997870. The cubic root of 1561778400 is about 1160.2185478037.

The spelling of 1561778400 in words is "one billion, five hundred sixty-one million, seven hundred seventy-eight thousand, four hundred".