21621887 has 6 divisors (see below), whose sum is σ = 25152048. Its totient is φ = 18533004.

The previous prime is 21621881. The next prime is 21621923. The reversal of 21621887 is 78812612.

It is not a de Polignac number, because 21621887 - 2⁴ = 21621871 is a prime.

It is a super-3 number, since 3×21621887³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21621881) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 220583 + ... + 220680.

It is an arithmetic number, because the mean of its divisors is an integer number (4192008).

Almost surely, 2^21621887 is an apocalyptic number.

21621887 is a deficient number, since it is larger than the sum of its proper divisors (3530161).

21621887 is an equidigital number, since it uses as much as digits as its factorization.

21621887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 441277 (or 441270 counting only the distinct ones).

The product of its digits is 10752, while the sum is 35.

The square root of 21621887 is about 4649.9340855543. The cubic root of 21621887 is about 278.5893634989.

The spelling of 21621887 in words is "twenty-one million, six hundred twenty-one thousand, eight hundred eighty-seven".