21157601 has 2 divisors, whose sum is σ = 21157602. Its totient is φ = 21157600.

The previous prime is 21157597. The next prime is 21157627. The reversal of 21157601 is 10675112.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20205025 + 952576 = 4495^2 + 976^2 .

It is a cyclic number.

It is not a de Polignac number, because 21157601 - 2² = 21157597 is a prime.

It is not a weakly prime, because it can be changed into another prime (21157901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10578800 + 10578801.

It is an arithmetic number, because the mean of its divisors is an integer number (10578801).

Almost surely, 2^21157601 is an apocalyptic number.

It is an amenable number.

21157601 is a deficient number, since it is larger than the sum of its proper divisors (1).

21157601 is an equidigital number, since it uses as much as digits as its factorization.

21157601 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 23.

The square root of 21157601 is about 4599.7392317391. The cubic root of 21157601 is about 276.5808716088.

The spelling of 21157601 in words is "twenty-one million, one hundred fifty-seven thousand, six hundred one".