21520373 has 16 divisors (see below), whose sum is σ = 25296000. Its totient is φ = 17928000.

The previous prime is 21520363. The next prime is 21520391. The reversal of 21520373 is 37302512.

It is a cyclic number.

It is not a de Polignac number, because 21520373 - 2¹⁰ = 21519349 is a prime.

It is a super-4 number, since 4×21520373⁴ (a number of 30 digits) contains 4444 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21520363) 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, 42878 + ... + 43376.

It is an arithmetic number, because the mean of its divisors is an integer number (1581000).

Almost surely, 2^21520373 is an apocalyptic number.

It is an amenable number.

21520373 is a deficient number, since it is larger than the sum of its proper divisors (3775627).

21520373 is a wasteful number, since it uses less digits than its factorization.

21520373 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 668.

The product of its (nonzero) digits is 1260, while the sum is 23.

The square root of 21520373 is about 4639.0056046528. The cubic root of 21520373 is about 278.1526903037.

Adding to 21520373 its reverse (37302512), we get a palindrome (58822885).

The spelling of 21520373 in words is "twenty-one million, five hundred twenty thousand, three hundred seventy-three".