645819551 has 8 divisors (see below), whose sum is σ = 695751504. Its totient is φ = 595923840.

The previous prime is 645819547. The next prime is 645819563. The reversal of 645819551 is 155918546.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 645819551 - 2² = 645819547 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645819541) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36455 + ... + 51191.

It is an arithmetic number, because the mean of its divisors is an integer number (86968938).

Almost surely, 2^645819551 is an apocalyptic number.

645819551 is a deficient number, since it is larger than the sum of its proper divisors (49931953).

645819551 is a wasteful number, since it uses less digits than its factorization.

645819551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18121.

The product of its digits is 216000, while the sum is 44.

The square root of 645819551 is about 25412.9799708732. The cubic root of 645819551 is about 864.3780491319.

The spelling of 645819551 in words is "six hundred forty-five million, eight hundred nineteen thousand, five hundred fifty-one".