21137810 has 16 divisors (see below), whose sum is σ = 39360600. Its totient is φ = 8163456.

The previous prime is 21137801. The next prime is 21137813. The reversal of 21137810 is 1873112.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 20241001 + 896809 = 4499^2 + 947^2 .

It is a super-3 number, since 3×21137810³ (a number of 23 digits) contains 333 as substring. Note that it is a super-d number also for d = 2.

It is not an unprimeable number, because it can be changed into a prime (21137813) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 36155 + ... + 36734.

Almost surely, 2^21137810 is an apocalyptic number.

21137810 is a deficient number, since it is larger than the sum of its proper divisors (18222790).

21137810 is a wasteful number, since it uses less digits than its factorization.

21137810 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72925.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 21137810 is about 4597.5874108058. The cubic root of 21137810 is about 276.4946060051.

The spelling of 21137810 in words is "twenty-one million, one hundred thirty-seven thousand, eight hundred ten".