21030557 has 2 divisors, whose sum is σ = 21030558. Its totient is φ = 21030556.

The previous prime is 21030553. The next prime is 21030589. The reversal of 21030557 is 75503012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18783556 + 2247001 = 4334^2 + 1499^2 .

It is a cyclic number.

It is not a de Polignac number, because 21030557 - 2² = 21030553 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21030551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10515278 + 10515279.

It is an arithmetic number, because the mean of its divisors is an integer number (10515279).

Almost surely, 2^21030557 is an apocalyptic number.

It is an amenable number.

21030557 is a deficient number, since it is larger than the sum of its proper divisors (1).

21030557 is an equidigital number, since it uses as much as digits as its factorization.

21030557 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1050, while the sum is 23.

The square root of 21030557 is about 4585.9085250362. The cubic root of 21030557 is about 276.0261693663.

Adding to 21030557 its reverse (75503012), we get a palindrome (96533569).

The spelling of 21030557 in words is "twenty-one million, thirty thousand, five hundred fifty-seven".