21122551 has 4 divisors (see below), whose sum is σ = 22365072. Its totient is φ = 19880032.

The previous prime is 21122473. The next prime is 21122561. The reversal of 21122551 is 15522112.

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 21122551 - 2¹¹ = 21120503 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 (21122561) 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, 621235 + ... + 621268.

It is an arithmetic number, because the mean of its divisors is an integer number (5591268).

Almost surely, 2^21122551 is an apocalyptic number.

21122551 is a deficient number, since it is larger than the sum of its proper divisors (1242521).

21122551 is a wasteful number, since it uses less digits than its factorization.

21122551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1242520.

The product of its digits is 200, while the sum is 19.

The square root of 21122551 is about 4595.9276539128. The cubic root of 21122551 is about 276.4280578494.

Adding to 21122551 its reverse (15522112), we get a palindrome (36644663).

The spelling of 21122551 in words is "twenty-one million, one hundred twenty-two thousand, five hundred fifty-one".