21121321204045 has 4 divisors (see below), whose sum is σ = 25345585444860. Its totient is φ = 16897056963232.

The previous prime is 21121321204043. The next prime is 21121321204097. The reversal of 21121321204045 is 54040212312112.

It is a happy number.

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 2435637786409 + 18685683417636 = 1560653^2 + 4322694^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121321204045 - 2¹ = 21121321204043 is a prime.

It is a super-2 number, since 2×21121321204045² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121321204043) 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, 2112132120400 + ... + 2112132120409.

It is an arithmetic number, because the mean of its divisors is an integer number (6336396361215).

Almost surely, 2^{21121321204045} is an apocalyptic number.

It is an amenable number.

21121321204045 is a deficient number, since it is larger than the sum of its proper divisors (4224264240815).

21121321204045 is an equidigital number, since it uses as much as digits as its factorization.

21121321204045 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4224264240814.

The product of its (nonzero) digits is 3840, while the sum is 28.

Adding to 21121321204045 its reverse (54040212312112), we get a palindrome (75161533516157).

The spelling of 21121321204045 in words is "twenty-one trillion, one hundred twenty-one billion, three hundred twenty-one million, two hundred four thousand, forty-five".