21351563 has 2 divisors, whose sum is σ = 21351564. Its totient is φ = 21351562.

The previous prime is 21351509. The next prime is 21351571. The reversal of 21351563 is 36515312.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21351563 - 2¹² = 21347467 is a prime.

It is not a weakly prime, because it can be changed into another prime (21351503) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10675781 + 10675782.

It is an arithmetic number, because the mean of its divisors is an integer number (10675782).

Almost surely, 2^21351563 is an apocalyptic number.

21351563 is a deficient number, since it is larger than the sum of its proper divisors (1).

21351563 is an equidigital number, since it uses as much as digits as its factorization.

21351563 is an evil number, because the sum of its binary digits is even.

The product of its digits is 2700, while the sum is 26.

The square root of 21351563 is about 4620.7751514221. The cubic root of 21351563 is about 277.4234856548.

Adding to 21351563 its reverse (36515312), we get a palindrome (57866875).

The spelling of 21351563 in words is "twenty-one million, three hundred fifty-one thousand, five hundred sixty-three".