20918729 has 16 divisors (see below), whose sum is σ = 23263632. Its totient is φ = 18690048.

The previous prime is 20918701. The next prime is 20918741. The reversal of 20918729 is 92781902.

20918729 = T₃₆₄ + T₃₆₅ + ... + T₅₅₇.

It can be written as a sum of positive squares in 8 ways, for example, as 4108729 + 16810000 = 2027^2 + 4100^2 .

It is not a de Polignac number, because 20918729 - 2¹⁶ = 20853193 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 20918692 and 20918701.

It is not an unprimeable number, because it can be changed into a prime (20918749) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 66677 + ... + 66989.

It is an arithmetic number, because the mean of its divisors is an integer number (1453977).

Almost surely, 2^20918729 is an apocalyptic number.

It is an amenable number.

20918729 is a deficient number, since it is larger than the sum of its proper divisors (2344903).

20918729 is a wasteful number, since it uses less digits than its factorization.

20918729 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 476.

The product of its (nonzero) digits is 18144, while the sum is 38.

The square root of 20918729 is about 4573.6997059274. The cubic root of 20918729 is about 275.5360519266.

The spelling of 20918729 in words is "twenty million, nine hundred eighteen thousand, seven hundred twenty-nine".