21969811 has 2 divisors, whose sum is σ = 21969812. Its totient is φ = 21969810.

The previous prime is 21969781. The next prime is 21969817. The reversal of 21969811 is 11896912.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21969811 - 2¹¹ = 21967763 is a prime.

It is not a weakly prime, because it can be changed into another prime (21969817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10984905 + 10984906.

It is an arithmetic number, because the mean of its divisors is an integer number (10984906).

Almost surely, 2^21969811 is an apocalyptic number.

21969811 is a deficient number, since it is larger than the sum of its proper divisors (1).

21969811 is an equidigital number, since it uses as much as digits as its factorization.

21969811 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 7776, while the sum is 37.

The square root of 21969811 is about 4687.1964968412. The cubic root of 21969811 is about 280.0757065694.

The spelling of 21969811 in words is "twenty-one million, nine hundred sixty-nine thousand, eight hundred eleven".