21413551 has 4 divisors (see below), whose sum is σ = 22540600. Its totient is φ = 20286504.

The previous prime is 21413549. The next prime is 21413569. The reversal of 21413551 is 15531412.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21413551 - 2¹ = 21413549 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 (21413531) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 563496 + ... + 563533.

It is an arithmetic number, because the mean of its divisors is an integer number (5635150).

Almost surely, 2^21413551 is an apocalyptic number.

21413551 is a deficient number, since it is larger than the sum of its proper divisors (1127049).

21413551 is a wasteful number, since it uses less digits than its factorization.

21413551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1127048.

The product of its digits is 600, while the sum is 22.

The square root of 21413551 is about 4627.4778227453. The cubic root of 21413551 is about 277.6916988334.

Adding to 21413551 its reverse (15531412), we get a palindrome (36944963).

The spelling of 21413551 in words is "twenty-one million, four hundred thirteen thousand, five hundred fifty-one".