21297740 has 24 divisors (see below), whose sum is σ = 44906400. Its totient is φ = 8484608.

The previous prime is 21297733. The next prime is 21297751. The reversal of 21297740 is 4779212.

It is a junction number, because it is equal to n+sod(n) for n = 21297697 and 21297706.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 3236 + ... + 7284.

It is an arithmetic number, because the mean of its divisors is an integer number (1871100).

Almost surely, 2^21297740 is an apocalyptic number.

21297740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21297740 is an abundant number, since it is smaller than the sum of its proper divisors (23608660).

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

21297740 is a wasteful number, since it uses less digits than its factorization.

21297740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4321 (or 4319 counting only the distinct ones).

The product of its (nonzero) digits is 7056, while the sum is 32.

The square root of 21297740 is about 4614.9474536554. The cubic root of 21297740 is about 277.1901798850.

The spelling of 21297740 in words is "twenty-one million, two hundred ninety-seven thousand, seven hundred forty".