21137557 has 16 divisors (see below), whose sum is σ = 25692160. Its totient is φ = 16986672.

The previous prime is 21137551. The next prime is 21137563. The reversal of 21137557 is 75573112.

It is an interprime number because it is at equal distance from previous prime (21137551) and next prime (21137563).

It is a cyclic number.

It is not a de Polignac number, because 21137557 - 2⁷ = 21137429 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21137551) 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, 12928 + ... + 14470.

It is an arithmetic number, because the mean of its divisors is an integer number (1605760).

Almost surely, 2^21137557 is an apocalyptic number.

It is an amenable number.

21137557 is a deficient number, since it is larger than the sum of its proper divisors (4554603).

21137557 is a wasteful number, since it uses less digits than its factorization.

21137557 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1672.

The product of its digits is 7350, while the sum is 31.

The square root of 21137557 is about 4597.5598962928. The cubic root of 21137557 is about 276.4935028726.

The spelling of 21137557 in words is "twenty-one million, one hundred thirty-seven thousand, five hundred fifty-seven".