21657380 has 24 divisors (see below), whose sum is σ = 46540032. Its totient is φ = 8461152.

The previous prime is 21657367. The next prime is 21657401. The reversal of 21657380 is 8375612.

It is a happy number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 11732 + ... + 13451.

It is an arithmetic number, because the mean of its divisors is an integer number (1939168).

Almost surely, 2^21657380 is an apocalyptic number.

21657380 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21657380 is an abundant number, since it is smaller than the sum of its proper divisors (24882652).

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

21657380 is a wasteful number, since it uses less digits than its factorization.

21657380 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25235 (or 25233 counting only the distinct ones).

The product of its (nonzero) digits is 10080, while the sum is 32.

The square root of 21657380 is about 4653.7490263228. The cubic root of 21657380 is about 278.7417178661.

The spelling of 21657380 in words is "twenty-one million, six hundred fifty-seven thousand, three hundred eighty".