21021111220987 has 2 divisors, whose sum is σ = 21021111220988. Its totient is φ = 21021111220986.

The previous prime is 21021111220973. The next prime is 21021111221057. The reversal of 21021111220987 is 78902211112012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21021111220987 - 2¹⁵ = 21021111188219 is a prime.

It is not a weakly prime, because it can be changed into another prime (21021111200987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (31) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10510555610493 + 10510555610494.

It is an arithmetic number, because the mean of its divisors is an integer number (10510555610494).

Almost surely, 2^{21021111220987} is an apocalyptic number.

21021111220987 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021111220987 is an equidigital number, since it uses as much as digits as its factorization.

21021111220987 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 8064, while the sum is 37.

Adding to 21021111220987 its reverse (78902211112012), we get a palindrome (99923322332999).

The spelling of 21021111220987 in words is "twenty-one trillion, twenty-one billion, one hundred eleven million, two hundred twenty thousand, nine hundred eighty-seven".