21775491 has 12 divisors (see below), whose sum is σ = 32538480. Its totient is φ = 14016240.

The previous prime is 21775489. The next prime is 21775493. The reversal of 21775491 is 19457712.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (21775489) and next prime (21775493).

It is not a de Polignac number, because 21775491 - 2¹ = 21775489 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21775493) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 41455 + ... + 41976.

It is an arithmetic number, because the mean of its divisors is an integer number (2711540).

Almost surely, 2^21775491 is an apocalyptic number.

21775491 is a deficient number, since it is larger than the sum of its proper divisors (10762989).

21775491 is a wasteful number, since it uses less digits than its factorization.

21775491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 83466 (or 83463 counting only the distinct ones).

The product of its digits is 17640, while the sum is 36.

The square root of 21775491 is about 4666.4216483297. The cubic root of 21775491 is about 279.2475161191.

The spelling of 21775491 in words is "twenty-one million, seven hundred seventy-five thousand, four hundred ninety-one".