21779497 has 2 divisors, whose sum is σ = 21779498. Its totient is φ = 21779496.

The previous prime is 21779473. The next prime is 21779519. The reversal of 21779497 is 79497712.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19456921 + 2322576 = 4411^2 + 1524^2 .

It is a cyclic number.

It is not a de Polignac number, because 21779497 - 2¹¹ = 21777449 is a prime.

It is not a weakly prime, because it can be changed into another prime (21779447) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10889748 + 10889749.

It is an arithmetic number, because the mean of its divisors is an integer number (10889749).

Almost surely, 2^21779497 is an apocalyptic number.

It is an amenable number.

21779497 is a deficient number, since it is larger than the sum of its proper divisors (1).

21779497 is an equidigital number, since it uses as much as digits as its factorization.

21779497 is an evil number, because the sum of its binary digits is even.

The product of its digits is 222264, while the sum is 46.

The square root of 21779497 is about 4666.8508654123. The cubic root of 21779497 is about 279.2646392991.

The spelling of 21779497 in words is "twenty-one million, seven hundred seventy-nine thousand, four hundred ninety-seven".