21537131 has 16 divisors (see below), whose sum is σ = 28021248. Its totient is φ = 16051200.

The previous prime is 21537121. The next prime is 21537137. The reversal of 21537131 is 13173512.

It is not a de Polignac number, because 21537131 - 2¹⁰ = 21536107 is a prime.

It is a super-2 number, since 2×21537131² = 927696023422322, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21537097 and 21537106.

It is not an unprimeable number, because it can be changed into a prime (21537137) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4310 + ... + 7851.

It is an arithmetic number, because the mean of its divisors is an integer number (1751328).

Almost surely, 2^21537131 is an apocalyptic number.

21537131 is a deficient number, since it is larger than the sum of its proper divisors (6484117).

21537131 is a wasteful number, since it uses less digits than its factorization.

21537131 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12202.

The product of its digits is 630, while the sum is 23.

The square root of 21537131 is about 4640.8114592170. The cubic root of 21537131 is about 278.2248711063.

The spelling of 21537131 in words is "twenty-one million, five hundred thirty-seven thousand, one hundred thirty-one".