21553316 has 6 divisors (see below), whose sum is σ = 37718310. Its totient is φ = 10776656.

The previous prime is 21553309. The next prime is 21553319. The reversal of 21553316 is 61335512.

It can be written as a sum of positive squares in only one way, i.e., 21529600 + 23716 = 4640^2 + 154^2 .

It is not an unprimeable number, because it can be changed into a prime (21553319) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2694161 + ... + 2694168.

It is an arithmetic number, because the mean of its divisors is an integer number (6286385).

Almost surely, 2^21553316 is an apocalyptic number.

It is an amenable number.

21553316 is a deficient number, since it is larger than the sum of its proper divisors (16164994).

21553316 is a wasteful number, since it uses less digits than its factorization.

21553316 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5388333 (or 5388331 counting only the distinct ones).

The product of its digits is 2700, while the sum is 26.

The square root of 21553316 is about 4642.5549000523. The cubic root of 21553316 is about 278.2945483225.

Adding to 21553316 its reverse (61335512), we get a palindrome (82888828).

The spelling of 21553316 in words is "twenty-one million, five hundred fifty-three thousand, three hundred sixteen".