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21949 = 47467
BaseRepresentation
bin101010110111101
31010002221
411112331
51200244
6245341
7120664
oct52675
933087
1021949
1115544
1210851
139cb5
147ddb
156784
hex55bd

21949 has 4 divisors (see below), whose sum is σ = 22464. Its totient is φ = 21436.

The previous prime is 21943. The next prime is 21961. The reversal of 21949 is 94912.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21949 - 27 = 21821 is a prime.

It is a Duffinian number.

It is a plaindrome in base 16.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21943) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 187 + ... + 280.

It is an arithmetic number, because the mean of its divisors is an integer number (5616).

221949 is an apocalyptic number.

21949 is the 94-th heptagonal number.

It is an amenable number.

21949 is a deficient number, since it is larger than the sum of its proper divisors (515).

21949 is an equidigital number, since it uses as much as digits as its factorization.

21949 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 514.

The product of its digits is 648, while the sum is 25.

The square root of 21949 is about 148.1519490253. The cubic root of 21949 is about 27.9987244317.

It can be divided in two parts, 219 and 49, that multiplied together give a triangular number (10731 = T146).

The spelling of 21949 in words is "twenty-one thousand, nine hundred forty-nine".

Divisors: 1 47 467 21949