21997061 has 2 divisors, whose sum is σ = 21997062. Its totient is φ = 21997060.

The previous prime is 21997043. The next prime is 21997069. The reversal of 21997061 is 16079912.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21996100 + 961 = 4690^2 + 31^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21997061 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21997069) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10998530 + 10998531.

It is an arithmetic number, because the mean of its divisors is an integer number (10998531).

Almost surely, 2^21997061 is an apocalyptic number.

It is an amenable number.

21997061 is a deficient number, since it is larger than the sum of its proper divisors (1).

21997061 is an equidigital number, since it uses as much as digits as its factorization.

21997061 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 6804, while the sum is 35.

The square root of 21997061 is about 4690.1024509066. The cubic root of 21997061 is about 280.1914549438.

The spelling of 21997061 in words is "twenty-one million, nine hundred ninety-seven thousand, sixty-one".