21026551 has 16 divisors (see below), whose sum is σ = 26017600. Its totient is φ = 16547328.

The previous prime is 21026549. The next prime is 21026557. The reversal of 21026551 is 15562012.

It is not a de Polignac number, because 21026551 - 2¹ = 21026549 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21026557) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 20335 + ... + 21343.

It is an arithmetic number, because the mean of its divisors is an integer number (1626100).

Almost surely, 2^21026551 is an apocalyptic number.

21026551 is a deficient number, since it is larger than the sum of its proper divisors (4991049).

21026551 is a wasteful number, since it uses less digits than its factorization.

21026551 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1258.

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

The square root of 21026551 is about 4585.4717314580. The cubic root of 21026551 is about 276.0086419964.

Adding to 21026551 its reverse (15562012), we get a palindrome (36588563).

The spelling of 21026551 in words is "twenty-one million, twenty-six thousand, five hundred fifty-one".