21024551 has 2 divisors, whose sum is σ = 21024552. Its totient is φ = 21024550.

The previous prime is 21024539. The next prime is 21024569. The reversal of 21024551 is 15542012.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21024551 - 2¹⁸ = 20762407 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21024581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10512275 + 10512276.

It is an arithmetic number, because the mean of its divisors is an integer number (10512276).

Almost surely, 2^21024551 is an apocalyptic number.

21024551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21024551 is an equidigital number, since it uses as much as digits as its factorization.

21024551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 400, while the sum is 20.

The square root of 21024551 is about 4585.2536462010. The cubic root of 21024551 is about 275.9998906042. Note that the first 3 decimals are identical.

Adding to 21024551 its reverse (15542012), we get a palindrome (36566563).

The spelling of 21024551 in words is "twenty-one million, twenty-four thousand, five hundred fifty-one".