21777913 has 2 divisors, whose sum is σ = 21777914. Its totient is φ = 21777912.

The previous prime is 21777907. The next prime is 21777937. The reversal of 21777913 is 31977712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11202409 + 10575504 = 3347^2 + 3252^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21777913 is a prime.

It is not a weakly prime, because it can be changed into another prime (21777953) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10888956 + 10888957.

It is an arithmetic number, because the mean of its divisors is an integer number (10888957).

Almost surely, 2^21777913 is an apocalyptic number.

It is an amenable number.

21777913 is a deficient number, since it is larger than the sum of its proper divisors (1).

21777913 is an equidigital number, since it uses as much as digits as its factorization.

21777913 is an evil number, because the sum of its binary digits is even.

The product of its digits is 18522, while the sum is 37.

The square root of 21777913 is about 4666.6811547394. The cubic root of 21777913 is about 279.2578689267.

The spelling of 21777913 in words is "twenty-one million, seven hundred seventy-seven thousand, nine hundred thirteen".