21777751 has 2 divisors, whose sum is σ = 21777752. Its totient is φ = 21777750.

The previous prime is 21777727. The next prime is 21777773. The reversal of 21777751 is 15777712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21777751 - 2¹¹ = 21775703 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21777751.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21777551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10888875 + 10888876.

It is an arithmetic number, because the mean of its divisors is an integer number (10888876).

Almost surely, 2^21777751 is an apocalyptic number.

21777751 is a deficient number, since it is larger than the sum of its proper divisors (1).

21777751 is an equidigital number, since it uses as much as digits as its factorization.

21777751 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 24010, while the sum is 37.

The square root of 21777751 is about 4666.6637976182. The cubic root of 21777751 is about 279.2571764838.

The spelling of 21777751 in words is "twenty-one million, seven hundred seventy-seven thousand, seven hundred fifty-one".