21540769 has 2 divisors, whose sum is σ = 21540770. Its totient is φ = 21540768.

The previous prime is 21540763. The next prime is 21540773. The reversal of 21540769 is 96704512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17181025 + 4359744 = 4145^2 + 2088^2 .

It is a cyclic number.

It is not a de Polignac number, because 21540769 - 2¹¹ = 21538721 is a prime.

It is a super-2 number, since 2×21540769² = 928009458222722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21540763) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770384 + 10770385.

It is an arithmetic number, because the mean of its divisors is an integer number (10770385).

Almost surely, 2^21540769 is an apocalyptic number.

It is an amenable number.

21540769 is a deficient number, since it is larger than the sum of its proper divisors (1).

21540769 is an equidigital number, since it uses as much as digits as its factorization.

21540769 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 15120, while the sum is 34.

The square root of 21540769 is about 4641.2033999815. The cubic root of 21540769 is about 278.2405359147.

The spelling of 21540769 in words is "twenty-one million, five hundred forty thousand, seven hundred sixty-nine".