21258740 has 24 divisors (see below), whose sum is σ = 46184040. Its totient is φ = 8210048.

The previous prime is 21258733. The next prime is 21258751. The reversal of 21258740 is 4785212.

It can be written as a sum of positive squares in 4 ways, for example, as 1669264 + 19589476 = 1292^2 + 4426^2 .

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 17747 + ... + 18906.

It is an arithmetic number, because the mean of its divisors is an integer number (1924335).

Almost surely, 2^21258740 is an apocalyptic number.

21258740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21258740 is an abundant number, since it is smaller than the sum of its proper divisors (24925300).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21258740 is a wasteful number, since it uses less digits than its factorization.

21258740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36691 (or 36689 counting only the distinct ones).

The product of its (nonzero) digits is 4480, while the sum is 29.

The square root of 21258740 is about 4610.7201172919. The cubic root of 21258740 is about 277.0208814470.

The spelling of 21258740 in words is "twenty-one million, two hundred fifty-eight thousand, seven hundred forty".