21755651 has 2 divisors, whose sum is σ = 21755652. Its totient is φ = 21755650.

The previous prime is 21755633. The next prime is 21755653. The reversal of 21755651 is 15655712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21755651 - 2¹⁰ = 21754627 is a prime.

Together with 21755653, it forms a pair of twin primes.

It is a Chen prime.

It is equal to p_1374746 and since 21755651 and 1374746 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (21755653) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10877825 + 10877826.

It is an arithmetic number, because the mean of its divisors is an integer number (10877826).

Almost surely, 2^21755651 is an apocalyptic number.

21755651 is a deficient number, since it is larger than the sum of its proper divisors (1).

21755651 is an equidigital number, since it uses as much as digits as its factorization.

21755651 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10500, while the sum is 32.

The square root of 21755651 is about 4664.2953379905. The cubic root of 21755651 is about 279.1626813817.

The spelling of 21755651 in words is "twenty-one million, seven hundred fifty-five thousand, six hundred fifty-one".