645998028 has 48 divisors (see below), whose sum is σ = 1718771040. Its totient is φ = 187075584.

The previous prime is 645997921. The next prime is 645998029. The reversal of 645998028 is 820899546.

It is a Harshad number since it is a multiple of its sum of digits (51).

It is not an unprimeable number, because it can be changed into a prime (645998029) 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, 119143 + ... + 124446.

It is an arithmetic number, because the mean of its divisors is an integer number (35807730).

Almost surely, 2^645998028 is an apocalyptic number.

645998028 is a gapful number since it is divisible by the number (68) formed by its first and last digit.

It is an amenable number.

645998028 is an abundant number, since it is smaller than the sum of its proper divisors (1072773012).

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

645998028 is a wasteful number, since it uses less digits than its factorization.

645998028 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243626 (or 243624 counting only the distinct ones).

The product of its (nonzero) digits is 1244160, while the sum is 51.

The square root of 645998028 is about 25416.4912605969. The cubic root of 645998028 is about 864.4576675494.

It can be divided in two parts, 64599 and 8028, that added together give a palindrome (72627).

The spelling of 645998028 in words is "six hundred forty-five million, nine hundred ninety-eight thousand, twenty-eight".