21561279 has 4 divisors (see below), whose sum is σ = 28748376. Its totient is φ = 14374184.

The previous prime is 21561277. The next prime is 21561311. The reversal of 21561279 is 97216512.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21561279 - 2¹ = 21561277 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21561277) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3593544 + ... + 3593549.

It is an arithmetic number, because the mean of its divisors is an integer number (7187094).

Almost surely, 2^21561279 is an apocalyptic number.

21561279 is a deficient number, since it is larger than the sum of its proper divisors (7187097).

21561279 is an equidigital number, since it uses as much as digits as its factorization.

21561279 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7187096.

The product of its digits is 7560, while the sum is 33.

The square root of 21561279 is about 4643.4124305299. The cubic root of 21561279 is about 278.3288166246.

The spelling of 21561279 in words is "twenty-one million, five hundred sixty-one thousand, two hundred seventy-nine".