21216223053261 has 24 divisors (see below), whose sum is σ = 30771308766744. Its totient is φ = 14086239020160.

The previous prime is 21216223053217. The next prime is 21216223053299. The reversal of 21216223053261 is 16235032261212.

21216223053261 is a `hidden beast` number, since 2 + 1 + 2 + 1 + 6 + 22 + 305 + 326 + 1 = 666.

It can be written as a sum of positive squares in 4 ways, for example, as 51567597225 + 21164655456036 = 227085^2 + 4600506^2 .

It is not a de Polignac number, because 21216223053261 - 2²⁶ = 21216155944397 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21216223053061) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 477426 + ... + 6531491.

It is an arithmetic number, because the mean of its divisors is an integer number (1282137865281).

Almost surely, 2^{21216223053261} is an apocalyptic number.

It is an amenable number.

21216223053261 is a deficient number, since it is larger than the sum of its proper divisors (9555085713483).

21216223053261 is a wasteful number, since it uses less digits than its factorization.

21216223053261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7010301 (or 7010298 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 36.

The spelling of 21216223053261 in words is "twenty-one trillion, two hundred sixteen billion, two hundred twenty-three million, fifty-three thousand, two hundred sixty-one".