21981079 has 2 divisors, whose sum is σ = 21981080. Its totient is φ = 21981078.

The previous prime is 21981059. The next prime is 21981107. The reversal of 21981079 is 97018912.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21981079 - 2¹⁹ = 21456791 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21981059) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10990539 + 10990540.

It is an arithmetic number, because the mean of its divisors is an integer number (10990540).

Almost surely, 2^21981079 is an apocalyptic number.

21981079 is a deficient number, since it is larger than the sum of its proper divisors (1).

21981079 is an equidigital number, since it uses as much as digits as its factorization.

21981079 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 9072, while the sum is 37.

The square root of 21981079 is about 4688.3983405850. The cubic root of 21981079 is about 280.1235806526.

The spelling of 21981079 in words is "twenty-one million, nine hundred eighty-one thousand, seventy-nine".