645261 has 4 divisors (see below), whose sum is σ = 860352. Its totient is φ = 430172.

The previous prime is 645257. The next prime is 645313. The reversal of 645261 is 162546.

645261 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 645261 - 2² = 645257 is a prime.

It is an Ulam number.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (645661) 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, 107541 + ... + 107546.

It is an arithmetic number, because the mean of its divisors is an integer number (215088).

2⁶⁴⁵²⁶¹ is an apocalyptic number.

It is an amenable number.

645261 is a deficient number, since it is larger than the sum of its proper divisors (215091).

645261 is a wasteful number, since it uses less digits than its factorization.

645261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 215090.

The product of its digits is 1440, while the sum is 24.

The square root of 645261 is about 803.2813952781. The cubic root of 645261 is about 86.4128785244.

The spelling of 645261 in words is "six hundred forty-five thousand, two hundred sixty-one".