21693977 has 2 divisors, whose sum is σ = 21693978. Its totient is φ = 21693976.

The previous prime is 21693967. The next prime is 21694007. The reversal of 21693977 is 77939612.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20620681 + 1073296 = 4541^2 + 1036^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21693977 is a prime.

It is not a weakly prime, because it can be changed into another prime (21693937) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10846988 + 10846989.

It is an arithmetic number, because the mean of its divisors is an integer number (10846989).

Almost surely, 2^21693977 is an apocalyptic number.

It is an amenable number.

21693977 is a deficient number, since it is larger than the sum of its proper divisors (1).

21693977 is an equidigital number, since it uses as much as digits as its factorization.

21693977 is an evil number, because the sum of its binary digits is even.

The product of its digits is 142884, while the sum is 44.

The square root of 21693977 is about 4657.6793577918. The cubic root of 21693977 is about 278.8986369707.

The spelling of 21693977 in words is "twenty-one million, six hundred ninety-three thousand, nine hundred seventy-seven".