21921155 has 16 divisors (see below), whose sum is σ = 28166400. Its totient is φ = 16328160.

The previous prime is 21921121. The next prime is 21921167. The reversal of 21921155 is 55112912.

It is not a de Polignac number, because 21921155 - 2¹⁶ = 21855619 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3650 + ... + 7560.

It is an arithmetic number, because the mean of its divisors is an integer number (1760400).

Almost surely, 2^21921155 is an apocalyptic number.

21921155 is a deficient number, since it is larger than the sum of its proper divisors (6245245).

21921155 is a wasteful number, since it uses less digits than its factorization.

21921155 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3994.

The product of its digits is 900, while the sum is 26.

The square root of 21921155 is about 4682.0033105499. The cubic root of 21921155 is about 279.8687948207.

The spelling of 21921155 in words is "twenty-one million, nine hundred twenty-one thousand, one hundred fifty-five".