21661045251355 has 16 divisors (see below), whose sum is σ = 26851461366528. Its totient is φ = 16757519616000.

The previous prime is 21661045251347. The next prime is 21661045251359. The reversal of 21661045251355 is 55315254016612.

It is a happy number.

It is not a de Polignac number, because 21661045251355 - 2³ = 21661045251347 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21661045251359) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 51129486 + ... + 51551395.

It is an arithmetic number, because the mean of its divisors is an integer number (1678216335408).

Almost surely, 2^{21661045251355} is an apocalyptic number.

21661045251355 is a deficient number, since it is larger than the sum of its proper divisors (5190416115173).

21661045251355 is a wasteful number, since it uses less digits than its factorization.

21661045251355 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 102682278.

The product of its (nonzero) digits is 1080000, while the sum is 46.

Adding to 21661045251355 its reverse (55315254016612), we get a palindrome (76976299267967).

The spelling of 21661045251355 in words is "twenty-one trillion, six hundred sixty-one billion, forty-five million, two hundred fifty-one thousand, three hundred fifty-five".