21255231024561 has 8 divisors (see below), whose sum is σ = 28342812302464. Its totient is φ = 14168901881520.

The previous prime is 21255231024553. The next prime is 21255231024569. The reversal of 21255231024561 is 16542013255212.

It is an interprime number because it is at equal distance from previous prime (21255231024553) and next prime (21255231024569).

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

It is not a de Polignac number, because 21255231024561 - 2³ = 21255231024553 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21255231024569) 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, 312994105 + ... + 313062006.

It is an arithmetic number, because the mean of its divisors is an integer number (3542851537808).

Almost surely, 2^{21255231024561} is an apocalyptic number.

It is an amenable number.

21255231024561 is a deficient number, since it is larger than the sum of its proper divisors (7087581277903).

21255231024561 is a wasteful number, since it uses less digits than its factorization.

21255231024561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 626067431.

The product of its (nonzero) digits is 144000, while the sum is 39.

Adding to 21255231024561 its reverse (16542013255212), we get a palindrome (37797244279773).

The spelling of 21255231024561 in words is "twenty-one trillion, two hundred fifty-five billion, two hundred thirty-one million, twenty-four thousand, five hundred sixty-one".