21047940 has 36 divisors (see below), whose sum is σ = 63845964. Its totient is φ = 5612736.

The previous prime is 21047927. The next prime is 21047951. The reversal of 21047940 is 4974012.

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 13660416 + 7387524 = 3696^2 + 2718^2 .

It is a tau number, because it is divible by the number of its divisors (36).

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 58287 + ... + 58646.

It is an arithmetic number, because the mean of its divisors is an integer number (1773499).

Almost surely, 2^21047940 is an apocalyptic number.

21047940 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21047940 is an abundant number, since it is smaller than the sum of its proper divisors (42798024).

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

21047940 is a wasteful number, since it uses less digits than its factorization.

21047940 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 116948 (or 116943 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 21047940 is about 4587.8033959619. The cubic root of 21047940 is about 276.1021990774.

The spelling of 21047940 in words is "twenty-one million, forty-seven thousand, nine hundred forty".