21121152243561 has 36 divisors (see below), whose sum is σ = 31272310540380. Its totient is φ = 13736577024000.

The previous prime is 21121152243539. The next prime is 21121152243563. The reversal of 21121152243561 is 16534225112112.

21121152243561 is a `hidden beast` number, since 2 + 1 + 1 + 2 + 1 + 1 + 52 + 2 + 43 + 561 = 666.

It can be written as a sum of positive squares in 6 ways, for example, as 13599544315536 + 7521607928025 = 3687756^2 + 2742555^2 .

It is not a de Polignac number, because 21121152243561 - 2¹³ = 21121152235369 is a prime.

It is a super-2 number, since 2×21121152243561² (a number of 27 digits) contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21121152243563) by changing a digit.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 441758025 + ... + 441805833.

Almost surely, 2^{21121152243561} is an apocalyptic number.

It is an amenable number.

21121152243561 is a deficient number, since it is larger than the sum of its proper divisors (10151158296819).

21121152243561 is a wasteful number, since it uses less digits than its factorization.

21121152243561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 77098 (or 77054 counting only the distinct ones).

The product of its digits is 28800, while the sum is 36.

Adding to 21121152243561 its reverse (16534225112112), we get a palindrome (37655377355673).

It can be divided in two parts, 2112115 and 2243561, that added together give a triangular number (4355676 = T₂₉₅₁).

The spelling of 21121152243561 in words is "twenty-one trillion, one hundred twenty-one billion, one hundred fifty-two million, two hundred forty-three thousand, five hundred sixty-one".