20971661 has 2 divisors, whose sum is σ = 20971662. Its totient is φ = 20971660.

The previous prime is 20971651. The next prime is 20971667. The reversal of 20971661 is 16617902.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14969161 + 6002500 = 3869^2 + 2450^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-20971661 is a prime.

It is a super-3 number, since 3×20971661³ (a number of 23 digits) contains 333 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20971667) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10485830 + 10485831.

It is an arithmetic number, because the mean of its divisors is an integer number (10485831).

Almost surely, 2^20971661 is an apocalyptic number.

It is an amenable number.

20971661 is a deficient number, since it is larger than the sum of its proper divisors (1).

20971661 is an equidigital number, since it uses as much as digits as its factorization.

20971661 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4536, while the sum is 32.

The square root of 20971661 is about 4579.4826126976. The cubic root of 20971661 is about 275.7682583551.

The spelling of 20971661 in words is "twenty million, nine hundred seventy-one thousand, six hundred sixty-one".