21065120253 has 20 divisors (see below), whose sum is σ = 32552743740. Its totient is φ = 13559156352.

The previous prime is 21065120249. The next prime is 21065120267. The reversal of 21065120253 is 35202156012.

It is a happy number.

21065120253 is a `hidden beast` number, since 2 + 1 + 0 + 651 + 2 + 0 + 2 + 5 + 3 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 3315686724 + 17749433529 = 57582^2 + 133227^2 .

It is not a de Polignac number, because 21065120253 - 2² = 21065120249 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21065120213) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 4481500 + ... + 4486197.

It is an arithmetic number, because the mean of its divisors is an integer number (1627637187).

Almost surely, 2^21065120253 is an apocalyptic number.

It is an amenable number.

21065120253 is a deficient number, since it is larger than the sum of its proper divisors (11487623487).

21065120253 is an equidigital number, since it uses as much as digits as its factorization.

21065120253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8967738 (or 8967729 counting only the distinct ones).

The product of its (nonzero) digits is 3600, while the sum is 27.

Adding to 21065120253 its reverse (35202156012), we get a palindrome (56267276265).

The spelling of 21065120253 in words is "twenty-one billion, sixty-five million, one hundred twenty thousand, two hundred fifty-three".