21630557 has 16 divisors (see below), whose sum is σ = 24665088. Its totient is φ = 18817920.

The previous prime is 21630551. The next prime is 21630563. The reversal of 21630557 is 75503612.

It is an interprime number because it is at equal distance from previous prime (21630551) and next prime (21630563).

It is a cyclic number.

It is not a de Polignac number, because 21630557 - 2⁴ = 21630541 is a prime.

It is a super-2 number, since 2×21630557² = 935761992260498, 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 (21630551) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 21332 + ... + 22322.

It is an arithmetic number, because the mean of its divisors is an integer number (1541568).

Almost surely, 2^21630557 is an apocalyptic number.

It is an amenable number.

21630557 is a deficient number, since it is larger than the sum of its proper divisors (3034531).

21630557 is a wasteful number, since it uses less digits than its factorization.

21630557 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1100.

The product of its (nonzero) digits is 6300, while the sum is 29.

The square root of 21630557 is about 4650.8662633965. The cubic root of 21630557 is about 278.6265950167.

The spelling of 21630557 in words is "twenty-one million, six hundred thirty thousand, five hundred fifty-seven".