1561978720 has 48 divisors (see below), whose sum is σ = 3724071120. Its totient is φ = 619052544.

The previous prime is 1561978703. The next prime is 1561978729. The reversal of 1561978720 is 278791651.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561978729) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27342 + ... + 62221.

It is an arithmetic number, because the mean of its divisors is an integer number (77584815).

Almost surely, 2^1561978720 is an apocalyptic number.

1561978720 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1561978720 is an abundant number, since it is smaller than the sum of its proper divisors (2162092400).

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

1561978720 is a wasteful number, since it uses less digits than its factorization.

1561978720 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 89687 (or 89679 counting only the distinct ones).

The product of its (nonzero) digits is 211680, while the sum is 46.

The square root of 1561978720 is about 39521.8764736696. The cubic root of 1561978720 is about 1160.2681504539.

The spelling of 1561978720 in words is "one billion, five hundred sixty-one million, nine hundred seventy-eight thousand, seven hundred twenty".