21945577 has 2 divisors, whose sum is σ = 21945578. Its totient is φ = 21945576.

The previous prime is 21945559. The next prime is 21945587. The reversal of 21945577 is 77554912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11048976 + 10896601 = 3324^2 + 3301^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21945577 is a prime.

It is not a weakly prime, because it can be changed into another prime (21945557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10972788 + 10972789.

It is an arithmetic number, because the mean of its divisors is an integer number (10972789).

Almost surely, 2^21945577 is an apocalyptic number.

It is an amenable number.

21945577 is a deficient number, since it is larger than the sum of its proper divisors (1).

21945577 is an equidigital number, since it uses as much as digits as its factorization.

21945577 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 88200, while the sum is 40.

The square root of 21945577 is about 4684.6106561805. The cubic root of 21945577 is about 279.9726886627.

It can be divided in two parts, 21945 and 577, that added together give a palindrome (22522).

The spelling of 21945577 in words is "twenty-one million, nine hundred forty-five thousand, five hundred seventy-seven".