21551313 has 8 divisors (see below), whose sum is σ = 32840128. Its totient is φ = 12315024.

The previous prime is 21551303. The next prime is 21551317. The reversal of 21551313 is 31315512.

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

It is not a de Polignac number, because 21551313 - 2⁴ = 21551297 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (21), and also a Moran number because the ratio is a prime number: 1026253 = 21551313 / (2 + 1 + 5 + 5 + 1 + 3 + 1 + 3).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21551313.

It is not an unprimeable number, because it can be changed into a prime (21551317) 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 7 ways as a sum of consecutive naturals, for example, 513106 + ... + 513147.

It is an arithmetic number, because the mean of its divisors is an integer number (4105016).

Almost surely, 2^21551313 is an apocalyptic number.

It is an amenable number.

21551313 is a deficient number, since it is larger than the sum of its proper divisors (11288815).

21551313 is a wasteful number, since it uses less digits than its factorization.

21551313 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1026263.

The product of its digits is 450, while the sum is 21.

The square root of 21551313 is about 4642.3391733048. The cubic root of 21551313 is about 278.2859272013.

Adding to 21551313 its reverse (31315512), we get a palindrome (52866825).

The spelling of 21551313 in words is "twenty-one million, five hundred fifty-one thousand, three hundred thirteen".