21511203125 has 42 divisors (see below), whose sum is σ = 27864838638. Its totient is φ = 16605400000.

The previous prime is 21511203071. The next prime is 21511203127. The reversal of 21511203125 is 52130211512.

It can be written as a sum of positive squares in 21 ways, for example, as 4439690161 + 17071512964 = 66631^2 + 130658^2 .

It is not a de Polignac number, because 21511203125 - 2¹⁰ = 21511202101 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21511203125.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21511203127) by changing a digit.

It is a polite number, since it can be written in 41 ways as a sum of consecutive naturals, for example, 13139807 + ... + 13141443.

It is an arithmetic number, because the mean of its divisors is an integer number (663448539).

Almost surely, 2^21511203125 is an apocalyptic number.

21511203125 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21511203125 is a deficient number, since it is larger than the sum of its proper divisors (6353635513).

21511203125 is an frugal number, since it uses more digits than its factorization.

21511203125 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1725 (or 1671 counting only the distinct ones).

The product of its (nonzero) digits is 600, while the sum is 23.

Adding to 21511203125 its reverse (52130211512), we get a palindrome (73641414637).

The spelling of 21511203125 in words is "twenty-one billion, five hundred eleven million, two hundred three thousand, one hundred twenty-five".