21672640 has 112 divisors (see below), whose sum is σ = 57936384. Its totient is φ = 7654400.

The previous prime is 21672631. The next prime is 21672649. The reversal of 21672640 is 4627612.

It is an interprime number because it is at equal distance from previous prime (21672631) and next prime (21672649).

It is a junction number, because it is equal to n+sod(n) for n = 21672599 and 21672608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21672649) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 165375 + ... + 165505.

Almost surely, 2^21672640 is an apocalyptic number.

21672640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21672640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28968192).

21672640 is an abundant number, since it is smaller than the sum of its proper divisors (36263744).

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

21672640 is a wasteful number, since it uses less digits than its factorization.

21672640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 206 (or 196 counting only the distinct ones).

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 21672640 is about 4655.3882759658. The cubic root of 21672640 is about 278.8071705349.

The spelling of 21672640 in words is "twenty-one million, six hundred seventy-two thousand, six hundred forty".