78405561 has 24 divisors (see below), whose sum is σ = 122411016. Its totient is φ = 48072960.

The previous prime is 78405527. The next prime is 78405599. The reversal of 78405561 is 16550487.

It can be written as a sum of positive squares in 4 ways, for example, as 1299600 + 77105961 = 1140^2 + 8781^2 .

It is not a de Polignac number, because 78405561 - 2¹⁵ = 78372793 is a prime.

It is a super-2 number, since 2×78405561² = 12294863991449442, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (78405521) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 35551 + ... + 37691.

It is an arithmetic number, because the mean of its divisors is an integer number (5100459).

Almost surely, 2^78405561 is an apocalyptic number.

It is an amenable number.

78405561 is a deficient number, since it is larger than the sum of its proper divisors (44005455).

78405561 is a wasteful number, since it uses less digits than its factorization.

78405561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2473 (or 2470 counting only the distinct ones).

The product of its (nonzero) digits is 33600, while the sum is 36.

The square root of 78405561 is about 8854.6914683686. The cubic root of 78405561 is about 428.0051113752.

The spelling of 78405561 in words is "seventy-eight million, four hundred five thousand, five hundred sixty-one".