21909771 has 20 divisors (see below), whose sum is σ = 35248752. Its totient is φ = 13482288.

The previous prime is 21909743. The next prime is 21909799. The reversal of 21909771 is 17790912.

It is an interprime number because it is at equal distance from previous prime (21909743) and next prime (21909799).

It is not a de Polignac number, because 21909771 - 2⁶ = 21909707 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21908771) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 9351 + ... + 11456.

Almost surely, 2^21909771 is an apocalyptic number.

21909771 is a deficient number, since it is larger than the sum of its proper divisors (13338981).

21909771 is a wasteful number, since it uses less digits than its factorization.

21909771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20832 (or 20823 counting only the distinct ones).

The product of its (nonzero) digits is 7938, while the sum is 36.

The square root of 21909771 is about 4680.7874337551. The cubic root of 21909771 is about 279.8203396787.

The spelling of 21909771 in words is "twenty-one million, nine hundred nine thousand, seven hundred seventy-one".