21142757 has 4 divisors (see below), whose sum is σ = 21658476. Its totient is φ = 20627040.

The previous prime is 21142753. The next prime is 21142777. The reversal of 21142757 is 75724112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 9541921 + 11600836 = 3089^2 + 3406^2 .

It is a cyclic number.

It is not a de Polignac number, because 21142757 - 2² = 21142753 is a prime.

It is a super-2 number, since 2×21142757² = 894032347122098, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21142753) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 257798 + ... + 257879.

It is an arithmetic number, because the mean of its divisors is an integer number (5414619).

Almost surely, 2^21142757 is an apocalyptic number.

It is an amenable number.

21142757 is a deficient number, since it is larger than the sum of its proper divisors (515719).

21142757 is an equidigital number, since it uses as much as digits as its factorization.

21142757 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 515718.

The product of its digits is 3920, while the sum is 29.

The square root of 21142757 is about 4598.1253788908. The cubic root of 21142757 is about 276.5161741828.

Adding to 21142757 its reverse (75724112), we get a palindrome (96866869).

The spelling of 21142757 in words is "twenty-one million, one hundred forty-two thousand, seven hundred fifty-seven".