21100657 has 2 divisors, whose sum is σ = 21100658. Its totient is φ = 21100656.

The previous prime is 21100649. The next prime is 21100687. The reversal of 21100657 is 75600112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19368801 + 1731856 = 4401^2 + 1316^2 .

It is a cyclic number.

It is not a de Polignac number, because 21100657 - 2³ = 21100649 is a prime.

It is not a weakly prime, because it can be changed into another prime (21100687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10550328 + 10550329.

It is an arithmetic number, because the mean of its divisors is an integer number (10550329).

Almost surely, 2^21100657 is an apocalyptic number.

It is an amenable number.

21100657 is a deficient number, since it is larger than the sum of its proper divisors (1).

21100657 is an equidigital number, since it uses as much as digits as its factorization.

21100657 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 420, while the sum is 22.

The square root of 21100657 is about 4593.5451450922. The cubic root of 21100657 is about 276.3325168617.

Adding to 21100657 its reverse (75600112), we get a palindrome (96700769).

The spelling of 21100657 in words is "twenty-one million, one hundred thousand, six hundred fifty-seven".