21155221253 has 8 divisors (see below), whose sum is σ = 21386753856. Its totient is φ = 20924892000.

The previous prime is 21155221187. The next prime is 21155221259. The reversal of 21155221253 is 35212255112.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21155221253 - 2⁸ = 21155220997 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 (21155221259) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 265463 + ... + 335828.

It is an arithmetic number, because the mean of its divisors is an integer number (2673344232).

Almost surely, 2^21155221253 is an apocalyptic number.

It is an amenable number.

21155221253 is a deficient number, since it is larger than the sum of its proper divisors (231532603).

21155221253 is a wasteful number, since it uses less digits than its factorization.

21155221253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 601675.

The product of its digits is 6000, while the sum is 29.

Adding to 21155221253 its reverse (35212255112), we get a palindrome (56367476365).

The spelling of 21155221253 in words is "twenty-one billion, one hundred fifty-five million, two hundred twenty-one thousand, two hundred fifty-three".