21077561 has 2 divisors, whose sum is σ = 21077562. Its totient is φ = 21077560.

The previous prime is 21077549. The next prime is 21077599. The reversal of 21077561 is 16577012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20529961 + 547600 = 4531^2 + 740^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21077561 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21007561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10538780 + 10538781.

It is an arithmetic number, because the mean of its divisors is an integer number (10538781).

Almost surely, 2^21077561 is an apocalyptic number.

It is an amenable number.

21077561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21077561 is an equidigital number, since it uses as much as digits as its factorization.

21077561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2940, while the sum is 29.

The square root of 21077561 is about 4591.0304943444. The cubic root of 21077561 is about 276.2316589312.

The spelling of 21077561 in words is "twenty-one million, seventy-seven thousand, five hundred sixty-one".