21006989 has 8 divisors (see below), whose sum is σ = 22321440. Its totient is φ = 19713456.

The previous prime is 21006977. The next prime is 21007001. The reversal of 21006989 is 98960012.

It is an interprime number because it is at equal distance from previous prime (21006977) and next prime (21007001).

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21006989 is a prime.

It is a super-2 number, since 2×21006989² = 882587173692242, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21006959) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3134 + ... + 7199.

It is an arithmetic number, because the mean of its divisors is an integer number (2790180).

Almost surely, 2^21006989 is an apocalyptic number.

It is an amenable number.

21006989 is a deficient number, since it is larger than the sum of its proper divisors (1314451).

21006989 is a wasteful number, since it uses less digits than its factorization.

21006989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10459.

The product of its (nonzero) digits is 7776, while the sum is 35.

The square root of 21006989 is about 4583.3381939368. The cubic root of 21006989 is about 275.9230207847.

The spelling of 21006989 in words is "twenty-one million, six thousand, nine hundred eighty-nine".