645321620 has 12 divisors (see below), whose sum is σ = 1355175444. Its totient is φ = 258128640.

The previous prime is 645321619. The next prime is 645321631. The reversal of 645321620 is 26123546.

It can be written as a sum of positive squares in 2 ways, for example, as 347897104 + 297424516 = 18652^2 + 17246^2 .

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 16133021 + ... + 16133060.

It is an arithmetic number, because the mean of its divisors is an integer number (112931287).

Almost surely, 2^645321620 is an apocalyptic number.

It is an amenable number.

645321620 is an abundant number, since it is smaller than the sum of its proper divisors (709853824).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

645321620 is a wasteful number, since it uses less digits than its factorization.

645321620 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 32266090 (or 32266088 counting only the distinct ones).

The product of its (nonzero) digits is 8640, while the sum is 29.

The square root of 645321620 is about 25403.1812968376. The cubic root of 645321620 is about 864.1558450157.

The spelling of 645321620 in words is "six hundred forty-five million, three hundred twenty-one thousand, six hundred twenty".