5638721021 has 16 divisors (see below), whose sum is σ = 5969291328. Its totient is φ = 5319888000.

The previous prime is 5638720993. The next prime is 5638721027. The reversal of 5638721021 is 1201278365.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 5638721021 - 2⁶ = 5638720957 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 (5638721027) 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, 162230 + ... + 193896.

It is an arithmetic number, because the mean of its divisors is an integer number (373080708).

Almost surely, 2^5638721021 is an apocalyptic number.

It is an amenable number.

5638721021 is a deficient number, since it is larger than the sum of its proper divisors (330570307).

5638721021 is a wasteful number, since it uses less digits than its factorization.

5638721021 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31852.

The product of its (nonzero) digits is 20160, while the sum is 35.

The square root of 5638721021 is about 75091.4177586227. The cubic root of 5638721021 is about 1779.8915286549.

Adding to 5638721021 its reverse (1201278365), we get a palindrome (6839999386).

The spelling of 5638721021 in words is "five billion, six hundred thirty-eight million, seven hundred twenty-one thousand, twenty-one".