21787340 has 24 divisors (see below), whose sum is σ = 46185552. Its totient is φ = 8632640.

The previous prime is 21787313. The next prime is 21787373. The reversal of 21787340 is 4378712.

It is a happy number.

It is a junction number, because it is equal to n+sod(n) for n = 21787297 and 21787306.

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, 2951 + ... + 7230.

It is an arithmetic number, because the mean of its divisors is an integer number (1924398).

Almost surely, 2^21787340 is an apocalyptic number.

21787340 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21787340 is an abundant number, since it is smaller than the sum of its proper divisors (24398212).

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

21787340 is a wasteful number, since it uses less digits than its factorization.

21787340 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10297 (or 10295 counting only the distinct ones).

The product of its (nonzero) digits is 9408, while the sum is 32.

The square root of 21787340 is about 4667.6910780385. The cubic root of 21787340 is about 279.2981572098.

The spelling of 21787340 in words is "twenty-one million, seven hundred eighty-seven thousand, three hundred forty".