21535051251221 has 2 divisors, whose sum is σ = 21535051251222. Its totient is φ = 21535051251220.

The previous prime is 21535051251179. The next prime is 21535051251227. The reversal of 21535051251221 is 12215215053512.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 10944094610596 + 10590956640625 = 3308186^2 + 3254375^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21535051251221 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21535051251227) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10767525625610 + 10767525625611.

It is an arithmetic number, because the mean of its divisors is an integer number (10767525625611).

Almost surely, 2^{21535051251221} is an apocalyptic number.

It is an amenable number.

21535051251221 is a deficient number, since it is larger than the sum of its proper divisors (1).

21535051251221 is an equidigital number, since it uses as much as digits as its factorization.

21535051251221 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 30000, while the sum is 35.

The spelling of 21535051251221 in words is "twenty-one trillion, five hundred thirty-five billion, fifty-one million, two hundred fifty-one thousand, two hundred twenty-one".