21551279 has 16 divisors (see below), whose sum is σ = 22945920. Its totient is φ = 20217600.

The previous prime is 21551273. The next prime is 21551297. The reversal of 21551279 is 97215512.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 21551279 - 2¹⁶ = 21485743 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21551273) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 213329 + ... + 213429.

It is an arithmetic number, because the mean of its divisors is an integer number (1434120).

Almost surely, 2^21551279 is an apocalyptic number.

21551279 is a deficient number, since it is larger than the sum of its proper divisors (1394641).

21551279 is a wasteful number, since it uses less digits than its factorization.

21551279 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 290.

The product of its digits is 6300, while the sum is 32.

The square root of 21551279 is about 4642.3355113563. The cubic root of 21551279 is about 278.2857808572.

The spelling of 21551279 in words is "twenty-one million, five hundred fifty-one thousand, two hundred seventy-nine".