645121003 has 4 divisors (see below), whose sum is σ = 679074760. Its totient is φ = 611167248.

The previous prime is 645120991. The next prime is 645121051. The reversal of 645121003 is 300121546.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 300121546 = 2 ⋅150060773.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-645121003 is a prime.

It is a super-2 number, since 2×645121003² = 832362217023452018, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (645121063) 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, 16976850 + ... + 16976887.

It is an arithmetic number, because the mean of its divisors is an integer number (169768690).

Almost surely, 2^645121003 is an apocalyptic number.

645121003 is a deficient number, since it is larger than the sum of its proper divisors (33953757).

645121003 is a wasteful number, since it uses less digits than its factorization.

645121003 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 33953756.

The product of its (nonzero) digits is 720, while the sum is 22.

The square root of 645121003 is about 25399.2323309190. The cubic root of 645121003 is about 864.0662864060.

Adding to 645121003 its reverse (300121546), we get a palindrome (945242549).

The spelling of 645121003 in words is "six hundred forty-five million, one hundred twenty-one thousand, three".