21742890 has 64 divisors (see below), whose sum is σ = 56681856. Its totient is φ = 5306112.

The previous prime is 21742829. The next prime is 21742913. The reversal of 21742890 is 9824712.

It is a happy number.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 76689 + ... + 76971.

It is an arithmetic number, because the mean of its divisors is an integer number (885654).

Almost surely, 2^21742890 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21742890, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28340928).

21742890 is an abundant number, since it is smaller than the sum of its proper divisors (34938966).

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

21742890 is a wasteful number, since it uses less digits than its factorization.

21742890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 503.

The product of its (nonzero) digits is 8064, while the sum is 33.

The square root of 21742890 is about 4662.9271922259. The cubic root of 21742890 is about 279.1080887960.

The spelling of 21742890 in words is "twenty-one million, seven hundred forty-two thousand, eight hundred ninety".