21787925 has 6 divisors (see below), whose sum is σ = 27017058. Its totient is φ = 17430320.

The previous prime is 21787907. The next prime is 21787939. The reversal of 21787925 is 52978712.

It can be written as a sum of positive squares in 3 ways, for example, as 174724 + 21613201 = 418^2 + 4649^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21787925 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 435734 + ... + 435783.

It is an arithmetic number, because the mean of its divisors is an integer number (4502843).

Almost surely, 2^21787925 is an apocalyptic number.

21787925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21787925 is a deficient number, since it is larger than the sum of its proper divisors (5229133).

21787925 is an equidigital number, since it uses as much as digits as its factorization.

21787925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 871527 (or 871522 counting only the distinct ones).

The product of its digits is 70560, while the sum is 41.

The square root of 21787925 is about 4667.7537424333. The cubic root of 21787925 is about 279.3006569483.

The spelling of 21787925 in words is "twenty-one million, seven hundred eighty-seven thousand, nine hundred twenty-five".