21154905 has 16 divisors (see below), whose sum is σ = 37608960. Its totient is φ = 11282544.

The previous prime is 21154873. The next prime is 21154907. The reversal of 21154905 is 50945112.

It is not a de Polignac number, because 21154905 - 2⁵ = 21154873 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21154907) 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 15 ways as a sum of consecutive naturals, for example, 78217 + ... + 78486.

It is an arithmetic number, because the mean of its divisors is an integer number (2350560).

Almost surely, 2^21154905 is an apocalyptic number.

It is an amenable number.

21154905 is a deficient number, since it is larger than the sum of its proper divisors (16454055).

21154905 is a wasteful number, since it uses less digits than its factorization.

21154905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 156717 (or 156711 counting only the distinct ones).

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

The square root of 21154905 is about 4599.4461623113. The cubic root of 21154905 is about 276.5691233691.

The spelling of 21154905 in words is "twenty-one million, one hundred fifty-four thousand, nine hundred five".