645624451 has 4 divisors (see below), whose sum is σ = 645689304. Its totient is φ = 645559600.

The previous prime is 645624449. The next prime is 645624491. The reversal of 645624451 is 154426546.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 154426546 = 2 ⋅77213273.

It is a cyclic number.

It is not a de Polignac number, because 645624451 - 2¹ = 645624449 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 645624451.

It is not an unprimeable number, because it can be changed into a prime (645624401) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 14005 + ... + 38566.

It is an arithmetic number, because the mean of its divisors is an integer number (161422326).

Almost surely, 2^645624451 is an apocalyptic number.

645624451 is a deficient number, since it is larger than the sum of its proper divisors (64853).

645624451 is a wasteful number, since it uses less digits than its factorization.

645624451 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 64852.

The product of its digits is 115200, while the sum is 37.

The square root of 645624451 is about 25409.1410913474. The cubic root of 645624451 is about 864.2909984267.

The spelling of 645624451 in words is "six hundred forty-five million, six hundred twenty-four thousand, four hundred fifty-one".