21021211987 has 2 divisors, whose sum is σ = 21021211988. Its totient is φ = 21021211986.

The previous prime is 21021211961. The next prime is 21021212041. The reversal of 21021211987 is 78911212012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21021211987 - 2²³ = 21012823379 is a prime.

It is not a weakly prime, because it can be changed into another prime (21021211907) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510605993 + 10510605994.

It is an arithmetic number, because the mean of its divisors is an integer number (10510605994).

Almost surely, 2^21021211987 is an apocalyptic number.

21021211987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021211987 is an equidigital number, since it uses as much as digits as its factorization.

21021211987 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4032, while the sum is 34.

Adding to 21021211987 its reverse (78911212012), we get a palindrome (99932423999).

The spelling of 21021211987 in words is "twenty-one billion, twenty-one million, two hundred eleven thousand, nine hundred eighty-seven".