21577840 has 20 divisors (see below), whose sum is σ = 50168664. Its totient is φ = 8631104.

The previous prime is 21577817. The next prime is 21577859. The reversal of 21577840 is 4877512.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (20).

It is a junction number, because it is equal to n+sod(n) for n = 21577796 and 21577805.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 134782 + ... + 134941.

Almost surely, 2^21577840 is an apocalyptic number.

21577840 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21577840 is an abundant number, since it is smaller than the sum of its proper divisors (28590824).

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

21577840 is a wasteful number, since it uses less digits than its factorization.

21577840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 269736 (or 269730 counting only the distinct ones).

The product of its (nonzero) digits is 15680, while the sum is 34.

The square root of 21577840 is about 4645.1953672585. The cubic root of 21577840 is about 278.4000589025.

The spelling of 21577840 in words is "twenty-one million, five hundred seventy-seven thousand, eight hundred forty".