21670740 has 288 divisors, whose sum is σ = 85612800. Its totient is φ = 4572288.

The previous prime is 21670739. The next prime is 21670741. The reversal of 21670740 is 4707612.

It is an interprime number because it is at equal distance from previous prime (21670739) and next prime (21670741).

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 (21670741) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 1666974 + ... + 1666986.

Almost surely, 2^21670740 is an apocalyptic number.

21670740 is a gapful number since it is divisible by the number (20) 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 21670740, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (42806400).

21670740 is an abundant number, since it is smaller than the sum of its proper divisors (63942060).

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

21670740 is a wasteful number, since it uses less digits than its factorization.

21670740 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 58 (or 30 counting only the distinct ones).

The product of its (nonzero) digits is 2352, while the sum is 27.

The square root of 21670740 is about 4655.1842068816. The cubic root of 21670740 is about 278.7990227950.

It can be divided in two parts, 21 and 670740, that added together give a square (670761 = 819²).

The spelling of 21670740 in words is "twenty-one million, six hundred seventy thousand, seven hundred forty".