21512790 has 112 divisors (see below), whose sum is σ = 62799408. Its totient is φ = 5272128.

The previous prime is 21512789. The next prime is 21512801. The reversal of 21512790 is 9721512.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 55 ways as a sum of consecutive naturals, for example, 94657 + ... + 94883.

It is an arithmetic number, because the mean of its divisors is an integer number (560709).

Almost surely, 2^21512790 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21512790, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31399704).

21512790 is an abundant number, since it is smaller than the sum of its proper divisors (41286618).

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

21512790 is a wasteful number, since it uses less digits than its factorization.

21512790 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 265 (or 250 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 27.

The square root of 21512790 is about 4638.1882238650. The cubic root of 21512790 is about 278.1200161544.

The spelling of 21512790 in words is "twenty-one million, five hundred twelve thousand, seven hundred ninety".