21261740 has 12 divisors (see below), whose sum is σ = 44649696. Its totient is φ = 8504688.

The previous prime is 21261707. The next prime is 21261767. The reversal of 21261740 is 4716212.

It is a zygodrome in base 9.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 531524 + ... + 531563.

It is an arithmetic number, because the mean of its divisors is an integer number (3720808).

Almost surely, 2^21261740 is an apocalyptic number.

21261740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21261740 is an abundant number, since it is smaller than the sum of its proper divisors (23387956).

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

21261740 is a wasteful number, since it uses less digits than its factorization.

21261740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1063096 (or 1063094 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21261740 is about 4611.0454346059. The cubic root of 21261740 is about 277.0339117513.

Adding to 21261740 its reverse (4716212), we get a palindrome (25977952).

The spelling of 21261740 in words is "twenty-one million, two hundred sixty-one thousand, seven hundred forty".