21465551 has 4 divisors (see below), whose sum is σ = 21491400. Its totient is φ = 21439704.

The previous prime is 21465541. The next prime is 21465553. The reversal of 21465551 is 15556412.

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 21465551 - 2⁶ = 21465487 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21465553) 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, 11636 + ... + 13353.

It is an arithmetic number, because the mean of its divisors is an integer number (5372850).

Almost surely, 2^21465551 is an apocalyptic number.

21465551 is a deficient number, since it is larger than the sum of its proper divisors (25849).

21465551 is an equidigital number, since it uses as much as digits as its factorization.

21465551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25848.

The product of its digits is 6000, while the sum is 29.

The square root of 21465551 is about 4633.0930273415. The cubic root of 21465551 is about 277.9162964190.

The spelling of 21465551 in words is "twenty-one million, four hundred sixty-five thousand, five hundred fifty-one".