21710640 has 80 divisors (see below), whose sum is σ = 76923648. Its totient is φ = 4962048.

The previous prime is 21710639. The next prime is 21710669. The reversal of 21710640 is 4601712.

It is a tau number, because it is divible by the number of its divisors (80).

It is a Harshad number since it is a multiple of its sum of digits (21).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4782 + ... + 8141.

Almost surely, 2^21710640 is an apocalyptic number.

21710640 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21710640 is an abundant number, since it is smaller than the sum of its proper divisors (55213008).

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

21710640 is a wasteful number, since it uses less digits than its factorization.

21710640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12946 (or 12940 counting only the distinct ones).

The product of its (nonzero) digits is 336, while the sum is 21.

The square root of 21710640 is about 4659.4677807664. The cubic root of 21710640 is about 278.9700254279.

The spelling of 21710640 in words is "twenty-one million, seven hundred ten thousand, six hundred forty".