21350551 has 2 divisors, whose sum is σ = 21350552. Its totient is φ = 21350550.

The previous prime is 21350543. The next prime is 21350597. The reversal of 21350551 is 15505312.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21350551 - 2³ = 21350543 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21350501) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10675275 + 10675276.

It is an arithmetic number, because the mean of its divisors is an integer number (10675276).

Almost surely, 2^21350551 is an apocalyptic number.

21350551 is a deficient number, since it is larger than the sum of its proper divisors (1).

21350551 is an equidigital number, since it uses as much as digits as its factorization.

21350551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 750, while the sum is 22.

The square root of 21350551 is about 4620.6656446880. The cubic root of 21350551 is about 277.4191025721.

Adding to 21350551 its reverse (15505312), we get a palindrome (36855863).

The spelling of 21350551 in words is "twenty-one million, three hundred fifty thousand, five hundred fifty-one".