21770424 has 64 divisors (see below), whose sum is σ = 65133600. Its totient is φ = 6697728.

The previous prime is 21770423. The next prime is 21770429. The reversal of 21770424 is 42407712.

It is a happy number.

It is a super-2 number, since 2×21770424² = 947902722279552, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21770423) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1069 + ... + 6684.

Almost surely, 2^21770424 is an apocalyptic number.

21770424 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21770424, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32566800).

21770424 is an abundant number, since it is smaller than the sum of its proper divisors (43363176).

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

21770424 is a wasteful number, since it uses less digits than its factorization.

21770424 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7781 (or 7771 counting only the distinct ones).

The product of its (nonzero) digits is 3136, while the sum is 27.

The square root of 21770424 is about 4665.8786953799. The cubic root of 21770424 is about 279.2258548099.

The spelling of 21770424 in words is "twenty-one million, seven hundred seventy thousand, four hundred twenty-four".