21888690 has 64 divisors (see below), whose sum is σ = 56173824. Its totient is φ = 5439488.

The previous prime is 21888689. The next prime is 21888721. The reversal of 21888690 is 9688812.

It is a super-2 number, since 2×21888690² = 958229499832200, which contains 22 as substring.

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, 85042 + ... + 85298.

It is an arithmetic number, because the mean of its divisors is an integer number (877716).

Almost surely, 2^21888690 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21888690, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (28086912).

21888690 is an abundant number, since it is smaller than the sum of its proper divisors (34285134).

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

21888690 is a wasteful number, since it uses less digits than its factorization.

21888690 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 451.

The product of its (nonzero) digits is 55296, while the sum is 42.

The square root of 21888690 is about 4678.5350271212. The cubic root of 21888690 is about 279.7305656457.

It can be divided in two parts, 21888 and 690, that added together give a triangular number (22578 = T₂₁₂).

The spelling of 21888690 in words is "twenty-one million, eight hundred eighty-eight thousand, six hundred ninety".