1561861664 has 48 divisors (see below), whose sum is σ = 3417785280. Its totient is φ = 696533760.

The previous prime is 1561861663. The next prime is 1561861669. The reversal of 1561861664 is 4661681651.

It is a Harshad number since it is a multiple of its sum of digits (44).

It is not an unprimeable number, because it can be changed into a prime (1561861661) 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, 23204 + ... + 60515.

It is an arithmetic number, because the mean of its divisors is an integer number (71203860).

Almost surely, 2^1561861664 is an apocalyptic number.

It is an amenable number.

1561861664 is an abundant number, since it is smaller than the sum of its proper divisors (1855923616).

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

1561861664 is a wasteful number, since it uses less digits than its factorization.

1561861664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 83793 (or 83785 counting only the distinct ones).

The product of its digits is 207360, while the sum is 44.

The square root of 1561861664 is about 39520.3955445793. The cubic root of 1561861664 is about 1160.2391659060.

The spelling of 1561861664 in words is "one billion, five hundred sixty-one million, eight hundred sixty-one thousand, six hundred sixty-four".