645681619 has 16 divisors (see below), whose sum is σ = 711760896. Its totient is φ = 580867200.

The previous prime is 645681557. The next prime is 645681637. The reversal of 645681619 is 916186546.

It is a cyclic number.

It is not a de Polignac number, because 645681619 - 2⁹ = 645681107 is a prime.

It is a super-2 number, since 2×645681619² = 833809506228922322, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (645661619) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 497179 + ... + 498475.

It is an arithmetic number, because the mean of its divisors is an integer number (44485056).

Almost surely, 2^645681619 is an apocalyptic number.

645681619 is a deficient number, since it is larger than the sum of its proper divisors (66079277).

645681619 is a wasteful number, since it uses less digits than its factorization.

645681619 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1746.

The product of its digits is 311040, while the sum is 46.

The square root of 645681619 is about 25410.2660159236. The cubic root of 645681619 is about 864.3165077505.

The spelling of 645681619 in words is "six hundred forty-five million, six hundred eighty-one thousand, six hundred nineteen".