21121153541 has 4 divisors (see below), whose sum is σ = 21125158284. Its totient is φ = 21117148800.

The previous prime is 21121153517. The next prime is 21121153561. The reversal of 21121153541 is 14535112112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 10772364100 + 10348789441 = 103790^2 + 101729^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121153541 - 2²⁶ = 21054044677 is a prime.

It is a super-2 number, since 2×21121153541² (a number of 21 digits) contains 22 as substring.

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 21121153541.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121153561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1994450 + ... + 2005011.

It is an arithmetic number, because the mean of its divisors is an integer number (5281289571).

Almost surely, 2^21121153541 is an apocalyptic number.

It is an amenable number.

21121153541 is a deficient number, since it is larger than the sum of its proper divisors (4004743).

21121153541 is an equidigital number, since it uses as much as digits as its factorization.

21121153541 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4004742.

The product of its digits is 1200, while the sum is 26.

Adding to 21121153541 its reverse (14535112112), we get a palindrome (35656265653).

The spelling of 21121153541 in words is "twenty-one billion, one hundred twenty-one million, one hundred fifty-three thousand, five hundred forty-one".