21709770 has 64 divisors (see below), whose sum is σ = 54120960. Its totient is φ = 5570048.

The previous prime is 21709763. The next prime is 21709771. The reversal of 21709770 is 7790712.

It is a super-2 number, since 2×21709770² = 942628226905800, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21709771) 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, 125404 + ... + 125576.

It is an arithmetic number, because the mean of its divisors is an integer number (845640).

Almost surely, 2^21709770 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21709770, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27060480).

21709770 is an abundant number, since it is smaller than the sum of its proper divisors (32411190).

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

21709770 is a wasteful number, since it uses less digits than its factorization.

21709770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 319.

The product of its (nonzero) digits is 6174, while the sum is 33.

The square root of 21709770 is about 4659.3744215291. The cubic root of 21709770 is about 278.9662990344.

The spelling of 21709770 in words is "twenty-one million, seven hundred nine thousand, seven hundred seventy".