645904349 has 4 divisors (see below), whose sum is σ = 646020060. Its totient is φ = 645788640.

The previous prime is 645904319. The next prime is 645904379. The reversal of 645904349 is 943409546.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (645904319) and next prime (645904379).

It can be written as a sum of positive squares in 2 ways, for example, as 401200900 + 244703449 = 20030^2 + 15643^2 .

It is a cyclic number.

It is not a de Polignac number, because 645904349 - 2¹² = 645900253 is a prime.

It is a super-2 number, since 2×645904349² = 834384856114227602, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645904319) 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, 49034 + ... + 60795.

It is an arithmetic number, because the mean of its divisors is an integer number (161505015).

Almost surely, 2^645904349 is an apocalyptic number.

It is an amenable number.

645904349 is a deficient number, since it is larger than the sum of its proper divisors (115711).

645904349 is a wasteful number, since it uses less digits than its factorization.

645904349 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 115710.

The product of its (nonzero) digits is 466560, while the sum is 44.

The square root of 645904349 is about 25414.6483154892. The cubic root of 645904349 is about 864.4158792667.

The spelling of 645904349 in words is "six hundred forty-five million, nine hundred four thousand, three hundred forty-nine".