1645721263 has 8 divisors (see below), whose sum is σ = 1687061376. Its totient is φ = 1604438400.

The previous prime is 1645721251. The next prime is 1645721267. The reversal of 1645721263 is 3621275461.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1645721263 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1645721267) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 47170 + ... + 74272.

It is an arithmetic number, because the mean of its divisors is an integer number (210882672).

Almost surely, 2^1645721263 is an apocalyptic number.

1645721263 is a deficient number, since it is larger than the sum of its proper divisors (41340113).

1645721263 is a wasteful number, since it uses less digits than its factorization.

1645721263 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 28625.

The product of its digits is 60480, while the sum is 37.

The square root of 1645721263 is about 40567.4902230838. The cubic root of 1645721263 is about 1180.6434446756.

The spelling of 1645721263 in words is "one billion, six hundred forty-five million, seven hundred twenty-one thousand, two hundred sixty-three".