21515213611 has 2 divisors, whose sum is σ = 21515213612. Its totient is φ = 21515213610.

The previous prime is 21515213609. The next prime is 21515213627. The reversal of 21515213611 is 11631251512.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21515213611 - 2¹ = 21515213609 is a prime.

Together with 21515213609, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 21515213611.

It is not a weakly prime, because it can be changed into another prime (21515210611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10757606805 + 10757606806.

It is an arithmetic number, because the mean of its divisors is an integer number (10757606806).

Almost surely, 2^21515213611 is an apocalyptic number.

21515213611 is a deficient number, since it is larger than the sum of its proper divisors (1).

21515213611 is an equidigital number, since it uses as much as digits as its factorization.

21515213611 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1800, while the sum is 28.

The spelling of 21515213611 in words is "twenty-one billion, five hundred fifteen million, two hundred thirteen thousand, six hundred eleven".