21428320987 has 2 divisors, whose sum is σ = 21428320988. Its totient is φ = 21428320986.

The previous prime is 21428320891. The next prime is 21428320993. The reversal of 21428320987 is 78902382412.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21428320987 - 2³¹ = 19280837339 is a prime.

It is not a weakly prime, because it can be changed into another prime (21428320387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10714160493 + 10714160494.

It is an arithmetic number, because the mean of its divisors is an integer number (10714160494).

Almost surely, 2^21428320987 is an apocalyptic number.

21428320987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21428320987 is an equidigital number, since it uses as much as digits as its factorization.

21428320987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 387072, while the sum is 46.

The spelling of 21428320987 in words is "twenty-one billion, four hundred twenty-eight million, three hundred twenty thousand, nine hundred eighty-seven".