21609701 has 2 divisors, whose sum is σ = 21609702. Its totient is φ = 21609700.

The previous prime is 21609691. The next prime is 21609713. The reversal of 21609701 is 10790612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13764100 + 7845601 = 3710^2 + 2801^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21609701 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21609101) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10804850 + 10804851.

It is an arithmetic number, because the mean of its divisors is an integer number (10804851).

Almost surely, 2^21609701 is an apocalyptic number.

It is an amenable number.

21609701 is a deficient number, since it is larger than the sum of its proper divisors (1).

21609701 is an equidigital number, since it uses as much as digits as its factorization.

21609701 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 756, while the sum is 26.

The square root of 21609701 is about 4648.6235597217. The cubic root of 21609701 is about 278.5370164186.

The spelling of 21609701 in words is "twenty-one million, six hundred nine thousand, seven hundred one".