Search a number
-
+
21904813 = 724091093
BaseRepresentation
bin101001110001…
…1110110101101
31112012212202101
41103203312231
521101423223
62101255101
7354121300
oct123436655
945185671
1021904813
1111401457
127404491
1346cc438
142ca2b37
151dca4ad
hex14e3dad

21904813 has 12 divisors (see below), whose sum is σ = 25566780. Its totient is φ = 18712512.

The previous prime is 21904807. The next prime is 21904837. The reversal of 21904813 is 31840912.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 20958084 + 946729 = 4578^2 + 973^2 .

It is not a de Polignac number, because 21904813 - 25 = 21904781 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21904843) 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, 19495 + ... + 20587.

It is an arithmetic number, because the mean of its divisors is an integer number (2130565).

Almost surely, 221904813 is an apocalyptic number.

It is an amenable number.

21904813 is a deficient number, since it is larger than the sum of its proper divisors (3661967).

21904813 is a wasteful number, since it uses less digits than its factorization.

21904813 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1516 (or 1509 counting only the distinct ones).

The product of its (nonzero) digits is 1728, while the sum is 28.

The square root of 21904813 is about 4680.2577920452. The cubic root of 21904813 is about 279.7992310767.

The spelling of 21904813 in words is "twenty-one million, nine hundred four thousand, eight hundred thirteen".

Divisors: 1 7 49 409 1093 2863 7651 20041 53557 447037 3129259 21904813