21172436 has 24 divisors (see below), whose sum is σ = 39373320. Its totient is φ = 9942912.

The previous prime is 21172433. The next prime is 21172439. The reversal of 21172436 is 63427112.

It is an interprime number because it is at equal distance from previous prime (21172433) and next prime (21172439).

It can be written as a sum of positive squares in 4 ways, for example, as 5522500 + 15649936 = 2350^2 + 3956^2 .

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21172433) 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, 1826 + ... + 6758.

It is an arithmetic number, because the mean of its divisors is an integer number (1640555).

Almost surely, 2^21172436 is an apocalyptic number.

It is an amenable number.

21172436 is a deficient number, since it is larger than the sum of its proper divisors (18200884).

21172436 is a wasteful number, since it uses less digits than its factorization.

21172436 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5003 (or 5001 counting only the distinct ones).

The product of its digits is 2016, while the sum is 26.

The square root of 21172436 is about 4601.3515405802. The cubic root of 21172436 is about 276.6454995822.

Adding to 21172436 its reverse (63427112), we get a palindrome (84599548).

The spelling of 21172436 in words is "twenty-one million, one hundred seventy-two thousand, four hundred thirty-six".