21120001261 has 2 divisors, whose sum is σ = 21120001262. Its totient is φ = 21120001260.

The previous prime is 21120001219. The next prime is 21120001267. The reversal of 21120001261 is 16210002112.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16150597225 + 4969404036 = 127085^2 + 70494^2 .

It is a cyclic number.

It is not a de Polignac number, because 21120001261 - 2²¹ = 21117904109 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21120001267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10560000630 + 10560000631.

It is an arithmetic number, because the mean of its divisors is an integer number (10560000631).

Almost surely, 2^21120001261 is an apocalyptic number.

It is an amenable number.

21120001261 is a deficient number, since it is larger than the sum of its proper divisors (1).

21120001261 is an equidigital number, since it uses as much as digits as its factorization.

21120001261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48, while the sum is 16.

Adding to 21120001261 its reverse (16210002112), we get a palindrome (37330003373).

The spelling of 21120001261 in words is "twenty-one billion, one hundred twenty million, one thousand, two hundred sixty-one".