21621740 has 36 divisors (see below), whose sum is σ = 52821216. Its totient is φ = 7412832.

The previous prime is 21621737. The next prime is 21621757. The reversal of 21621740 is 4712612.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 10052 + ... + 12011.

It is an arithmetic number, because the mean of its divisors is an integer number (1467256).

Almost surely, 2^21621740 is an apocalyptic number.

21621740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21621740 is an abundant number, since it is smaller than the sum of its proper divisors (31199476).

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

21621740 is a wasteful number, since it uses less digits than its factorization.

21621740 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 22086 (or 22077 counting only the distinct ones).

The product of its (nonzero) digits is 672, while the sum is 23.

The square root of 21621740 is about 4649.9182788518. The cubic root of 21621740 is about 278.5887321520.

The spelling of 21621740 in words is "twenty-one million, six hundred twenty-one thousand, seven hundred forty".