641540721 has 16 divisors (see below), whose sum is σ = 870341120. Its totient is φ = 420232320.

The previous prime is 641540707. The next prime is 641540729. The reversal of 641540721 is 127045146.

It is not a de Polignac number, because 641540721 - 2¹⁰ = 641539697 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (641540729) 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, 320901 + ... + 322893.

It is an arithmetic number, because the mean of its divisors is an integer number (54396320).

Almost surely, 2^641540721 is an apocalyptic number.

641540721 is a gapful number since it is divisible by the number (61) formed by its first and last digit.

It is an amenable number.

641540721 is a deficient number, since it is larger than the sum of its proper divisors (228800399).

641540721 is a wasteful number, since it uses less digits than its factorization.

641540721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3816.

The product of its (nonzero) digits is 6720, while the sum is 30.

The square root of 641540721 is about 25328.6541490068. The cubic root of 641540721 is about 862.4648599000.

Adding to 641540721 its reverse (127045146), we get a palindrome (768585867).

The spelling of 641540721 in words is "six hundred forty-one million, five hundred forty thousand, seven hundred twenty-one".