645021023 has 2 divisors, whose sum is σ = 645021024. Its totient is φ = 645021022.

The previous prime is 645021019. The next prime is 645021029. The reversal of 645021023 is 320120546.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 645021023 - 2² = 645021019 is a prime.

It is a super-2 number, since 2×645021023² = 832104240223933058, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 645021023.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (645021029) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 322510511 + 322510512.

It is an arithmetic number, because the mean of its divisors is an integer number (322510512).

Almost surely, 2^645021023 is an apocalyptic number.

645021023 is a deficient number, since it is larger than the sum of its proper divisors (1).

645021023 is an equidigital number, since it uses as much as digits as its factorization.

645021023 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 23.

The square root of 645021023 is about 25397.2640849364. The cubic root of 645021023 is about 864.0216468163.

Adding to 645021023 its reverse (320120546), we get a palindrome (965141569).

The spelling of 645021023 in words is "six hundred forty-five million, twenty-one thousand, twenty-three".