987856921 has 2 divisors, whose sum is σ = 987856922. Its totient is φ = 987856920.

The previous prime is 987856879. The next prime is 987856967. The reversal of 987856921 is 129658789.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 774842896 + 213014025 = 27836^2 + 14595^2 .

It is a cyclic number.

It is not a de Polignac number, because 987856921 - 2⁹ = 987856409 is a prime.

It is a super-2 number, since 2×987856921² = 1951722592735200482, which contains 22 as substring.

It is an alternating number because its digits alternate between odd and even.

It is not a weakly prime, because it can be changed into another prime (987856981) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 493928460 + 493928461.

It is an arithmetic number, because the mean of its divisors is an integer number (493928461).

Almost surely, 2^987856921 is an apocalyptic number.

It is an amenable number.

987856921 is a deficient number, since it is larger than the sum of its proper divisors (1).

987856921 is an equidigital number, since it uses as much as digits as its factorization.

987856921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2177280, while the sum is 55.

The square root of 987856921 is about 31430.1912339076. The cubic root of 987856921 is about 995.9358117508.

The spelling of 987856921 in words is "nine hundred eighty-seven million, eight hundred fifty-six thousand, nine hundred twenty-one".