21609740 has 24 divisors (see below), whose sum is σ = 45626112. Its totient is φ = 8597120.

The previous prime is 21609733. The next prime is 21609767. The reversal of 21609740 is 4790612.

It is a congruent 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, 992 + ... + 6648.

It is an arithmetic number, because the mean of its divisors is an integer number (1901088).

Almost surely, 2^21609740 is an apocalyptic number.

21609740 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21609740 is an abundant number, since it is smaller than the sum of its proper divisors (24016372).

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

21609740 is a wasteful number, since it uses less digits than its factorization.

21609740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5857 (or 5855 counting only the distinct ones).

The product of its (nonzero) digits is 3024, while the sum is 29.

The square root of 21609740 is about 4648.6277545099. The cubic root of 21609740 is about 278.5371839812.

The spelling of 21609740 in words is "twenty-one million, six hundred nine thousand, seven hundred forty".