21787725 has 24 divisors (see below), whose sum is σ = 36158400. Its totient is φ = 11576320.

The previous prime is 21787723. The next prime is 21787741. The reversal of 21787725 is 52778712.

It is not a de Polignac number, because 21787725 - 2¹ = 21787723 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21787723) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 33352 + ... + 33998.

It is an arithmetic number, because the mean of its divisors is an integer number (1506600).

Almost surely, 2^21787725 is an apocalyptic number.

21787725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21787725 is a deficient number, since it is larger than the sum of its proper divisors (14370675).

21787725 is a wasteful number, since it uses less digits than its factorization.

21787725 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1109 (or 1104 counting only the distinct ones).

The product of its digits is 54880, while the sum is 39.

The square root of 21787725 is about 4667.7323188032. The cubic root of 21787725 is about 279.2998023419.

The spelling of 21787725 in words is "twenty-one million, seven hundred eighty-seven thousand, seven hundred twenty-five".