21316009 has 16 divisors (see below), whose sum is σ = 26135424. Its totient is φ = 17107200.

The previous prime is 21315997. The next prime is 21316021. The reversal of 21316009 is 90061312.

It is an interprime number because it is at equal distance from previous prime (21315997) and next prime (21316021).

It is not a de Polignac number, because 21316009 - 2¹⁹ = 20791721 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21316109) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 49 + ... + 6529.

It is an arithmetic number, because the mean of its divisors is an integer number (1633464).

Almost surely, 2^21316009 is an apocalyptic number.

It is an amenable number.

21316009 is a deficient number, since it is larger than the sum of its proper divisors (4819415).

21316009 is a wasteful number, since it uses less digits than its factorization.

21316009 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6528.

The product of its (nonzero) digits is 324, while the sum is 22.

The square root of 21316009 is about 4616.9263585204. The cubic root of 21316009 is about 277.2694142723.

It can be divided in two parts, 2131600 and 9, that multiplied together give a square (19184400 = 4380²).

The spelling of 21316009 in words is "twenty-one million, three hundred sixteen thousand, nine".