21909155 has 8 divisors (see below), whose sum is σ = 26322000. Its totient is φ = 17506656.

The previous prime is 21909131. The next prime is 21909161. The reversal of 21909155 is 55190912.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21909155 - 2⁸ = 21908899 is a prime.

It is a super-2 number, since 2×21909155² = 960022145628050, which contains 22 as substring.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 3296 + ... + 7394.

It is an arithmetic number, because the mean of its divisors is an integer number (3290250).

Almost surely, 2^21909155 is an apocalyptic number.

21909155 is a deficient number, since it is larger than the sum of its proper divisors (4412845).

21909155 is a wasteful number, since it uses less digits than its factorization.

21909155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5173.

The product of its (nonzero) digits is 4050, while the sum is 32.

The square root of 21909155 is about 4680.7216323981. The cubic root of 21909155 is about 279.8177172422.

The spelling of 21909155 in words is "twenty-one million, nine hundred nine thousand, one hundred fifty-five".