21111025 has 24 divisors (see below), whose sum is σ = 29857464. Its totient is φ = 14668800.

The previous prime is 21111007. The next prime is 21111029. The reversal of 21111025 is 52011112.

It can be written as a sum of positive squares in 12 ways, for example, as 2509056 + 18601969 = 1584^2 + 4313^2 .

It is not a de Polignac number, because 21111025 - 2⁹ = 21110513 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (13).

It is a junction number, because it is equal to n+sod(n) for n = 21110996 and 21111014.

It is not an unprimeable number, because it can be changed into a prime (21111029) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 3615 + ... + 7435.

It is an arithmetic number, because the mean of its divisors is an integer number (1244061).

Almost surely, 2^21111025 is an apocalyptic number.

21111025 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21111025 is a deficient number, since it is larger than the sum of its proper divisors (8746439).

21111025 is a wasteful number, since it uses less digits than its factorization.

21111025 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3861 (or 3856 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 13.

The square root of 21111025 is about 4594.6735466190. The cubic root of 21111025 is about 276.3777689505.

Adding to 21111025 its reverse (52011112), we get a palindrome (73122137).

It can be divided in two parts, 2111 and 1025, that added together give a square (3136 = 56²).

The spelling of 21111025 in words is "twenty-one million, one hundred eleven thousand, twenty-five".