21515534533 has 2 divisors, whose sum is σ = 21515534534. Its totient is φ = 21515534532.

The previous prime is 21515534519. The next prime is 21515534539. The reversal of 21515534533 is 33543551512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18248497569 + 3267036964 = 135087^2 + 57158^2 .

It is a cyclic number.

It is not a de Polignac number, because 21515534533 - 2⁵ = 21515534501 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21515534492 and 21515534501.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21515534539) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10757767266 + 10757767267.

It is an arithmetic number, because the mean of its divisors is an integer number (10757767267).

Almost surely, 2^21515534533 is an apocalyptic number.

It is an amenable number.

21515534533 is a deficient number, since it is larger than the sum of its proper divisors (1).

21515534533 is an equidigital number, since it uses as much as digits as its factorization.

21515534533 is an evil number, because the sum of its binary digits is even.

The product of its digits is 135000, while the sum is 37.

The spelling of 21515534533 in words is "twenty-one billion, five hundred fifteen million, five hundred thirty-four thousand, five hundred thirty-three".