21002989 has 16 divisors (see below), whose sum is σ = 25027200. Its totient is φ = 17244864.

The previous prime is 21002987. The next prime is 21003001. The reversal of 21002989 is 98920012.

21002989 = T₁₁₈₉ + T₁₁₉₀ + ... + T₁₂₁₇.

It is not a de Polignac number, because 21002989 - 2¹ = 21002987 is a prime.

It is a super-2 number, since 2×21002989² = 882251093868242, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21002989.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21002981) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 31542 + ... + 32200.

It is an arithmetic number, because the mean of its divisors is an integer number (1564200).

Almost surely, 2^21002989 is an apocalyptic number.

21002989 is a gapful number since it is divisible by the number (29) formed by its first and last digit.

It is an amenable number.

21002989 is a deficient number, since it is larger than the sum of its proper divisors (4024211).

21002989 is a wasteful number, since it uses less digits than its factorization.

21002989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 852.

The product of its (nonzero) digits is 2592, while the sum is 31.

The square root of 21002989 is about 4582.9018099890. The cubic root of 21002989 is about 275.9055065796.

The spelling of 21002989 in words is "twenty-one million, two thousand, nine hundred eighty-nine".