21757969 has 2 divisors, whose sum is σ = 21757970. Its totient is φ = 21757968.

The previous prime is 21757951. The next prime is 21757999. The reversal of 21757969 is 96975712.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21743569 + 14400 = 4663^2 + 120^2 .

It is a cyclic number.

It is not a de Polignac number, because 21757969 - 2⁹ = 21757457 is a prime.

It is a super-2 number, since 2×21757969² = 946818430009922, which contains 22 as substring.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21757999) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10878984 + 10878985.

It is an arithmetic number, because the mean of its divisors is an integer number (10878985).

Almost surely, 2^21757969 is an apocalyptic number.

It is an amenable number.

21757969 is a deficient number, since it is larger than the sum of its proper divisors (1).

21757969 is an equidigital number, since it uses as much as digits as its factorization.

21757969 is an evil number, because the sum of its binary digits is even.

The product of its digits is 238140, while the sum is 46.

The square root of 21757969 is about 4664.5438147797. The cubic root of 21757969 is about 279.1725956811.

The spelling of 21757969 in words is "twenty-one million, seven hundred fifty-seven thousand, nine hundred sixty-nine".