21457722 has 64 divisors (see below), whose sum is σ = 51166080. Its totient is φ = 5913600.

The previous prime is 21457721. The next prime is 21457727. The reversal of 21457722 is 22775412.

It is a self number, because there is not a number n which added to its sum of digits gives 21457722.

It is not an unprimeable number, because it can be changed into a prime (21457721) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 76222 + ... + 76502.

It is an arithmetic number, because the mean of its divisors is an integer number (799470).

Almost surely, 2^21457722 is an apocalyptic number.

21457722 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is a practical number, because each smaller number is the sum of distinct divisors of 21457722, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (25583040).

21457722 is an abundant number, since it is smaller than the sum of its proper divisors (29708358).

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

21457722 is a wasteful number, since it uses less digits than its factorization.

21457722 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 399.

The product of its digits is 7840, while the sum is 30.

The square root of 21457722 is about 4632.2480503531. The cubic root of 21457722 is about 277.8825047364.

The spelling of 21457722 in words is "twenty-one million, four hundred fifty-seven thousand, seven hundred twenty-two".