645724440421 has 16 divisors (see below), whose sum is σ = 685558427328. Its totient is φ = 606097273600.

The previous prime is 645724440409. The next prime is 645724440437. The reversal of 645724440421 is 124044427546.

It is not a de Polignac number, because 645724440421 - 2²¹ = 645722343269 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 (645724440461) 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, 17913306 + ... + 17949316.

It is an arithmetic number, because the mean of its divisors is an integer number (42847401708).

Almost surely, 2^645724440421 is an apocalyptic number.

It is an amenable number.

645724440421 is a deficient number, since it is larger than the sum of its proper divisors (39833986907).

645724440421 is a wasteful number, since it uses less digits than its factorization.

645724440421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 38852.

The product of its (nonzero) digits is 860160, while the sum is 43.

Adding to 645724440421 its reverse (124044427546), we get a palindrome (769768867967).

The spelling of 645724440421 in words is "six hundred forty-five billion, seven hundred twenty-four million, four hundred forty thousand, four hundred twenty-one".