21416551 has 16 divisors (see below), whose sum is σ = 23748480. Its totient is φ = 19192320.

The previous prime is 21416543. The next prime is 21416561. The reversal of 21416551 is 15561412.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21416551 - 2³ = 21416543 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21416531) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 89490 + ... + 89728.

It is an arithmetic number, because the mean of its divisors is an integer number (1484280).

Almost surely, 2^21416551 is an apocalyptic number.

21416551 is a deficient number, since it is larger than the sum of its proper divisors (2331929).

21416551 is a wasteful number, since it uses less digits than its factorization.

21416551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 426.

The product of its digits is 1200, while the sum is 25.

The square root of 21416551 is about 4627.8019620550. The cubic root of 21416551 is about 277.7046662638.

Adding to 21416551 its reverse (15561412), we get a palindrome (36977963).

The spelling of 21416551 in words is "twenty-one million, four hundred sixteen thousand, five hundred fifty-one".