1561640 has 16 divisors (see below), whose sum is σ = 3513780. Its totient is φ = 624640.

The previous prime is 1561639. The next prime is 1561657. The reversal of 1561640 is 461651.

It can be written as a sum of positive squares in 2 ways, for example, as 1503076 + 58564 = 1226^2 + 242^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 19481 + ... + 19560.

2^1561640 is an apocalyptic number.

1561640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1561640 is an abundant number, since it is smaller than the sum of its proper divisors (1952140).

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

1561640 is a wasteful number, since it uses less digits than its factorization.

1561640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 39052 (or 39048 counting only the distinct ones).

The product of its (nonzero) digits is 720, while the sum is 23.

The square root of 1561640 is about 1249.6559526526. The cubic root of 1561640 is about 116.0184275124.

The spelling of 1561640 in words is "one million, five hundred sixty-one thousand, six hundred forty".