21505927 has 2 divisors, whose sum is σ = 21505928. Its totient is φ = 21505926.

The previous prime is 21505903. The next prime is 21505949. The reversal of 21505927 is 72950512.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21505927 is a prime.

It is a super-2 number, since 2×21505927² = 925009792258658, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21503927) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10752963 + 10752964.

It is an arithmetic number, because the mean of its divisors is an integer number (10752964).

Almost surely, 2^21505927 is an apocalyptic number.

21505927 is a deficient number, since it is larger than the sum of its proper divisors (1).

21505927 is an equidigital number, since it uses as much as digits as its factorization.

21505927 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6300, while the sum is 31.

The square root of 21505927 is about 4637.4483285531. The cubic root of 21505927 is about 278.0904377706.

The spelling of 21505927 in words is "twenty-one million, five hundred five thousand, nine hundred twenty-seven".