21501372 has 48 divisors (see below), whose sum is σ = 52093440. Its totient is φ = 6897792.

The previous prime is 21501371. The next prime is 21501373. The reversal of 21501372 is 27310512.

It is an interprime number because it is at equal distance from previous prime (21501371) and next prime (21501373).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21501371) 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, 37504 + ... + 38072.

It is an arithmetic number, because the mean of its divisors is an integer number (1085280).

Almost surely, 2^21501372 is an apocalyptic number.

It is an amenable number.

21501372 is an abundant number, since it is smaller than the sum of its proper divisors (30592068).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21501372 is a wasteful number, since it uses less digits than its factorization.

21501372 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 690 (or 688 counting only the distinct ones).

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 21501372 is about 4636.9571919525. The cubic root of 21501372 is about 278.0708030069.

Adding to 21501372 its reverse (27310512), we get a palindrome (48811884).

The spelling of 21501372 in words is "twenty-one million, five hundred one thousand, three hundred seventy-two".