646401555 has 48 divisors (see below), whose sum is σ = 1135330560. Its totient is φ = 340200000.

The previous prime is 646401541. The next prime is 646401559. The reversal of 646401555 is 555104646.

646401555 is a `hidden beast` number, since 6 + 4 + 640 + 1 + 5 + 5 + 5 = 666.

It is not a de Polignac number, because 646401555 - 2⁹ = 646401043 is a prime.

It is not an unprimeable number, because it can be changed into a prime (646401559) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 1705356 + ... + 1705734.

It is an arithmetic number, because the mean of its divisors is an integer number (23652720).

Almost surely, 2^646401555 is an apocalyptic number.

646401555 is a deficient number, since it is larger than the sum of its proper divisors (488929005).

646401555 is a wasteful number, since it uses less digits than its factorization.

646401555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 792 (or 789 counting only the distinct ones).

The product of its (nonzero) digits is 72000, while the sum is 36.

The square root of 646401555 is about 25424.4283121568. The cubic root of 646401555 is about 864.6376265100.

The spelling of 646401555 in words is "six hundred forty-six million, four hundred one thousand, five hundred fifty-five".