21542220521 has 2 divisors, whose sum is σ = 21542220522. Its totient is φ = 21542220520.

The previous prime is 21542220457. The next prime is 21542220529. The reversal of 21542220521 is 12502224512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19884102121 + 1658118400 = 141011^2 + 40720^2 .

It is a cyclic number.

It is not a de Polignac number, because 21542220521 - 2⁶ = 21542220457 is a prime.

It is a super-2 number, since 2×21542220521² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21542220529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10771110260 + 10771110261.

It is an arithmetic number, because the mean of its divisors is an integer number (10771110261).

Almost surely, 2^21542220521 is an apocalyptic number.

It is an amenable number.

21542220521 is a deficient number, since it is larger than the sum of its proper divisors (1).

21542220521 is an equidigital number, since it uses as much as digits as its factorization.

21542220521 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 3200, while the sum is 26.

The spelling of 21542220521 in words is "twenty-one billion, five hundred forty-two million, two hundred twenty thousand, five hundred twenty-one".