21561373 has 8 divisors (see below), whose sum is σ = 22881600. Its totient is φ = 20273088.

The previous prime is 21561359. The next prime is 21561377. The reversal of 21561373 is 37316512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21561373 - 2⁵ = 21561341 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561377) 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, 6588 + ... + 9301.

It is an arithmetic number, because the mean of its divisors is an integer number (2860200).

Almost surely, 2^21561373 is an apocalyptic number.

21561373 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

It is an amenable number.

21561373 is a deficient number, since it is larger than the sum of its proper divisors (1320227).

21561373 is a wasteful number, since it uses less digits than its factorization.

21561373 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15971.

The product of its digits is 3780, while the sum is 28.

The square root of 21561373 is about 4643.4225523853. The cubic root of 21561373 is about 278.3292210977.

Adding to 21561373 its reverse (37316512), we get a palindrome (58877885).

The spelling of 21561373 in words is "twenty-one million, five hundred sixty-one thousand, three hundred seventy-three".