21016989 has 40 divisors (see below), whose sum is σ = 36334848. Its totient is φ = 11858400.

The previous prime is 21016979. The next prime is 21016993. The reversal of 21016989 is 98961012.

It is not a de Polignac number, because 21016989 - 2¹³ = 21008797 is a prime.

It is a super-4 number, since 4×21016989⁴ (a number of 30 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21016949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 57084 + ... + 57450.

Almost surely, 2^21016989 is an apocalyptic number.

It is an amenable number.

21016989 is a deficient number, since it is larger than the sum of its proper divisors (15317859).

21016989 is a wasteful number, since it uses less digits than its factorization.

21016989 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 487 (or 478 counting only the distinct ones).

The product of its (nonzero) digits is 7776, while the sum is 36.

The square root of 21016989 is about 4584.4289720749. The cubic root of 21016989 is about 275.9667965728.

The spelling of 21016989 in words is "twenty-one million, sixteen thousand, nine hundred eighty-nine".