21504542015401 has 9 divisors (see below), whose sum is σ = 21527916182199. Its totient is φ = 21481193214936.

The previous prime is 21504542015399. The next prime is 21504542015417. The reversal of 21504542015401 is 10451024540512.

The square root of 21504542015401 is 4637299.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 877285123225 + 20627256892176 = 936635^2 + 4541724^2 .

It is not a de Polignac number, because 21504542015401 - 2¹ = 21504542015399 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21504542015471) by changing a digit.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 5625041776 + ... + 5625045598.

It is an arithmetic number, because the mean of its divisors is an integer number (2391990686911).

Almost surely, 2^{21504542015401} is an apocalyptic number.

21504542015401 is the 4637299-th square number.

21504542015401 is the 2318650-th centered octagonal number.

It is an amenable number.

21504542015401 is a deficient number, since it is larger than the sum of its proper divisors (23374166798).

21504542015401 is an frugal number, since it uses more digits than its factorization.

21504542015401 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10072 (or 5036 counting only the distinct ones).

The product of its (nonzero) digits is 32000, while the sum is 34.

Adding to 21504542015401 its reverse (10451024540512), we get a palindrome (31955566555913).

The spelling of 21504542015401 in words is "twenty-one trillion, five hundred four billion, five hundred forty-two million, fifteen thousand, four hundred one".