21528926491 has 2 divisors, whose sum is σ = 21528926492. Its totient is φ = 21528926490.

The previous prime is 21528926479. The next prime is 21528926501. The reversal of 21528926491 is 19462982512.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21528926491 - 2⁵ = 21528926459 is a prime.

It is not a weakly prime, because it can be changed into another prime (21528926431) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10764463245 + 10764463246.

It is an arithmetic number, because the mean of its divisors is an integer number (10764463246).

Almost surely, 2^21528926491 is an apocalyptic number.

21528926491 is a deficient number, since it is larger than the sum of its proper divisors (1).

21528926491 is an equidigital number, since it uses as much as digits as its factorization.

21528926491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 622080, while the sum is 49.

The spelling of 21528926491 in words is "twenty-one billion, five hundred twenty-eight million, nine hundred twenty-six thousand, four hundred ninety-one".