21550491 has 6 divisors (see below), whose sum is σ = 31128500. Its totient is φ = 14366988.

The previous prime is 21550469. The next prime is 21550493. The reversal of 21550491 is 19405512.

21550491 is a `hidden beast` number, since 21 + 550 + 4 + 91 = 666.

It is not a de Polignac number, because 21550491 - 2¹³ = 21542299 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21550493) 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 5 ways as a sum of consecutive naturals, for example, 1197241 + ... + 1197258.

Almost surely, 2^21550491 is an apocalyptic number.

21550491 is a deficient number, since it is larger than the sum of its proper divisors (9578009).

21550491 is a wasteful number, since it uses less digits than its factorization.

21550491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2394505 (or 2394502 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 27.

The square root of 21550491 is about 4642.2506395067. The cubic root of 21550491 is about 278.2823890729.

The spelling of 21550491 in words is "twenty-one million, five hundred fifty thousand, four hundred ninety-one".