21216569 has 8 divisors (see below), whose sum is σ = 23289312. Its totient is φ = 19167840.

The previous prime is 21216553. The next prime is 21216607. The reversal of 21216569 is 96561212.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21216569 - 2⁴ = 21216553 is a prime.

It is a super-2 number, since 2×21216569² = 900285600263522, which contains 22 as substring.

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

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21216529) 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, 4124 + ... + 7709.

It is an arithmetic number, because the mean of its divisors is an integer number (2911164).

Almost surely, 2^21216569 is an apocalyptic number.

It is an amenable number.

21216569 is a deficient number, since it is larger than the sum of its proper divisors (2072743).

21216569 is a wasteful number, since it uses less digits than its factorization.

21216569 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12007.

The product of its digits is 6480, while the sum is 32.

The square root of 21216569 is about 4606.1447002890. The cubic root of 21216569 is about 276.8375845879.

The spelling of 21216569 in words is "twenty-one million, two hundred sixteen thousand, five hundred sixty-nine".