51621820 has 48 divisors (see below), whose sum is σ = 112896000. Its totient is φ = 19805760.

The previous prime is 51621811. The next prime is 51621833. The reversal of 51621820 is 2812615.

It is a super-2 number, since 2×51621820² = 5329624600224800, which contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 85881 + ... + 86479.

It is an arithmetic number, because the mean of its divisors is an integer number (2352000).

Almost surely, 2^51621820 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 51621820, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (56448000).

51621820 is an abundant number, since it is smaller than the sum of its proper divisors (61274180).

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

51621820 is a wasteful number, since it uses less digits than its factorization.

51621820 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 778 (or 776 counting only the distinct ones).

The product of its (nonzero) digits is 960, while the sum is 25.

The square root of 51621820 is about 7184.8326354898. The cubic root of 51621820 is about 372.3440663789.

It can be divided in two parts, 51621 and 820, that added together give a square (52441 = 229²).

The spelling of 51621820 in words is "fifty-one million, six hundred twenty-one thousand, eight hundred twenty".